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Synthesis of heteroboroxines with MB2O3 core (M = Sb, Bi, Sn)—an influence of the substitution of parent boronic acids† Monika Kořenková, Barbora Mairychová, Aleš Růžička, Roman Jambor* and Libor Dostál* The synthesis and structure of stiba-, stanna- and bismaheteroboroxines of a general formula L(E)M[(OBR)2O] supported by a N,C,N-chelating ligand L [where L = C6H3-2,6-(CH2NMe2)2, M, E = Sb, lone pair or Sn, Ph or Bi, lone pair] is reported. The target compounds are prepared by straightforward one-step reactions between oxides (LMO)2 (M = Sb or Bi) or organotin(IV) carbonate L(Ph)Sn(CO3) with four or two molar equivalents of corresponding organoboronic acid. All compounds were characterized with the help of elemental analysis, multinuclear NMR spectroscopy and on several occasions the molecular structure was determined using single-crystal X-ray diffraction analysis. The influence of both the substitution of the parent organoboronic acid and the central atom used on the feasibility of the condensation reaction was addressed. Furthermore, several heteroboroxines containing nitrogen donor functionality (i.e. NH2, NMe2, CN or 4-pyridyl) included in the boronic acid residue were synthesized and characterized with the

Received 25th October 2013, Accepted 13th February 2014 DOI: 10.1039/c3dt53012d www.rsc.org/dalton

aim to prepare boroxine-based covalent frameworks (through intermolecular N→B interactions) containing metal atoms in their structures. Although no such intermolecular bonding was detected in solution of these compounds, it was shown that the organotin(IV) heteroboroxine substituted by 4-pyridyl group forms an infinite polymeric chains via N→B interactions in the solid state. This polymer collapsed back to monomeric units upon dissolution.

Introduction Inorganic rings incorporating heavier main group elements have recently attracted considerable interest because of their unusual reactivity and unique structural features. These compounds may be formally formed by substitution of one (or more) lighter element (Si, Al, P etc.) in classical ring compounds such as cyclo-siloxanes,1 alumoxanes2 or various types of phosphorus containing cycles3 by heavier p-block element. It should be noted that synthesis of such mixed element inorganic rings often requires complicated experimental procedures (including difficult separation) and(or) preparation of various well-defined and sufficiently reactive intermediates. Nevertheless, it seems that the development in the chemistry of such inorganic rings has tremendously increased.

Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-532 10 Pardubice, Czech Republic. E-mail: [email protected]; Fax: +420 466037068; Tel: +420 466037163 † Electronic supplementary information (ESI) available: Crystallographic data for all compounds (Table S1) and Fig. S1 and S2 showing the molecular structures of 2b and 4a. CCDC 963753–963761. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3dt53012d

7096 | Dalton Trans., 2014, 43, 7096–7108

Boroxines constitute a well-established class among inorganic ring systems. The chemistry of these compounds featuring six-membered B3O3 core has undergone a period of renaissance4 due to their potential applications in material science5 and as reactants or catalysts in various organic transformation.6 Noteworthy, in contrast to before mentioned inorganic rings, the chemistry of so-called heteroboroxines (i.e. compounds where one or two boron atoms are replaced by another p-block element) seems to still be in its infancy.4 The known examples include several tin(IV) containing compounds Sn(t-Bu)2[OB(OH)Ph]2,7 Sn(t-Bu)2(OH)2[(t-Bu2SnO)2OBC6H2Me3-2,4,6]2·2MeCN or phosphorus(V) derived compounds supported by salen-like ligand.8 Also the chemistry of borasiloxanes has been developed to some extent.9 Significant breakthrough has been achieved by Roesky et al. in 2006 and later on, who reported on the conversion between either the aluminum(I) compound L′Al or the hydride L′AlH2 with respective boronic acid yielding alumaboroxines L′Al[(OBR)2O] [where L′ = HC(CMeNAr)2, Ar = 2,6-i-PrC6H3, and R = Ph, 3-MeC6H4, 3-FC6H4].10 We have recently developed a straightforward synthetic protocol for preparation of related heteroboroxines containing antimony(III), bismuth(III) and tin(IV) as heteroatoms within the

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Fig. 1

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Structure of already prepared heteroboroxines by our group.

MB2O3 core (Fig. 1), that is based on a simple and high yielding reaction between oxides (LSbO)2 and (LBiO)2 or the organotin(IV) carbonate L(Ph)Sn(CO3) and organoboronic acids.11 The common feature of these compounds is stabilization of the central metal (Sb, Bi, Sn) by a N,C,N-coordinating pincer-type ligand L [where L = C6H3-2,6-(CH2NMe2)2].12 It seemed to be reasonable to further develop the chemistry of related heteroboroxines and to investigate their reactivity. As the first contribution to this field, we report here on the preparation of a wider set of stiba-, bisma- and stannaboroxines targeting two main questions: (i) What influence has the position of the functional group (o- vs. m- vs. p- on the phenyl ring of the respective boronic acid) on the formation of expected heteroboroxines. To follow this trend, various sets of o-, m- and p-substituted organoboronic acids were tested in preparation of titled heteroboroxines; (ii) The boron atom is inherently Lewis acidic, even within the boroxine ring, and tends to form Lewis adducts especially with N-donors.13 This property has recently been utilized for preparation of a wide variety of interesting oligonuclear or polymeric species (materials) with specific properties and applications.4,14 Considering this fact, we have also synthesized a set of heteroboroxines containing N-donor functionality in boronic acid residues with the aim to check any possibility of formation of such N→B bonded oligomeric or polymeric species, that in one pot would embed heavier p-block element in their structure.

Results and discussion Influence of the substitution of parent boronic acids Studied heteroboroxines were prepared by the reaction of starting oxides (LMO)2 (M = Sb15 or Bi16) or tin carbonate L(Ph)Sn(CO3)17 with four or two molar equivalents of corresponding organoboronic acids (Schemes 1 and 2). To follow the influence of the substitution of boronic acids, two sets of o-, m- and p-substituted phenyl boronic acids (either with CF3 or Br group) were used in this study. The conversion between CF3substituted boronic acids and starting compounds smoothly gave expected heteroboroxines 1a–c,11 2a–c and 3a–c in satisfying to very good yields, but the situation with the Br-derived boronic acids was more complicated. While the p- and m-substituted acids produced expected heteroboroxines 4a–c and 5a–c (Schemes 1 and 2), using of the ortho isomer led only to the successful isolation of the organotin(IV) compound 6c

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Scheme 1 Preparation heteroboroxines.

Scheme 2

of

antimony

and

bismuth

containing

Preparation of tin containing heteroboroxines.

(Scheme 2). On the contrary, an analogous reaction in the case of antimony and bismuth compounds resulted only in complicated and non-separable mixture of products. This discrepancy in reactivity between (LMO)2 (M = Sb or Bi) and L(Ph)Sn(CO3) seems to be a general phenomenon. Thus, using of other o-substituted boronic acids (i.e. by CH3O or CHO functionalities) allowed successful isolation of intended heteroboroxines only in the case of the tin compounds (7c and 8c, Scheme 2), while similar reactions with antimony and bismuth oxides (LMO)2 (M = Sb or Bi) produced only mixtures of products. The identity of 1a–8c was unambiguously established by elemental analysis and 1H, 13C, 19F and 119Sn NMR spectroscopy (see the Experimental). All compounds were obtained as solids that are stable in air for a long time in the case of antimony compounds and under inert atmosphere in the case of tin and bismuth derivatives. All compounds are well soluble in chlorinated solvents, showed limited solubility in aromatic solvents and are nearly insoluble in aliphatic solvents. The 1H NMR spectra of 1a–8c revealed an AX spin system for methylene CH2N groups suggesting the presence of N→M intramolecular interactions with pseudo-facial type coordination of the CH2NMe2 arms of the ligand L. The 1H NMR spectra confirmed the presence of L and organic residues of

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Fig. 2 ORTEP plot of a molecule of 2a showing 30% probability displacement ellipsoid. Hydrogen atoms are omitted for clarity and only one of two independent molecules in the unit cell is presented. 2b is isostructural to 2a and its molecular structure is shown in Fig. S1.†

Fig. 3 ORTEP plot of a molecule of 3a showing 30% probability displacement ellipsoid. Hydrogen atoms are omitted for clarity.

organoboronic acids in 1 : 2 integral ratio corroborating the formation of six-membered heteroboroxine rings. An equivalence of boron-bonded substituents on the heteroboroxine ring was proven by the 1H and 13C NMR spectra of 1a–8c, where only one set of signals was observed. The presence of the CF3 moieties in respective heteroboroxines was established by the help of 19F NMR spectroscopy as well as by an observation of a typical quartet in the corresponding 13C NMR spectra with the 1JF–C ∼ 272 Hz. The 119Sn NMR spectra of tin compounds displayed a singlet in a narrow range from −360.1 (7c) to −369.2 (3c) which is indeed consistent with the presence of hexacoordinated tin atoms.18 The molecular structures of compounds 2a, 2b, 3a, 4a and 4b were unambiguously determined using single-crystal X-ray diffraction analysis and are shown in Fig. 2, S1,† 3, S2† and 4, respectively. Crystallographic data are summarized in Table S1 in the ESI† and selected structural parameters are summarized in Tables 1 and 2. Metal atoms are stabilized by a coordination of the NCN donor set of the ligand L. M–N distances [in the range of 2.596(4)–2.677(4) Å for M = Sb, 2.670(4)–2.704(4) Å for M = Bi] indicate the presence of N→M intramolecular

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Fig. 4 ORTEP plot of a molecule of 4b showing 30% probability displacement ellipsoid. The asymmetric unit is half of the molecule as this is found crystallized at a mirror plane. Symmetry operator a = x, 1/2 − y, z. Hydrogen atoms are omitted for clarity. 4a is isostructural to 4b and its molecular structure is shown in Fig. S2.†

interactions in all compounds as these values are significantly shorter than the ∑vdW(M, N) = 3.74 (Sb) and 3.94 Å (Bi).19 The coordination of the ligand L may be described as a pseudofacial as indicated by N–M–N bonding angles [in the range of 123.(4)–127.9(3)° in 2a, 2b, 3a, 4a and 4b]. The coordination polyhedron around central atoms may be best described as a strongly distorted octahedron in all cases, where both nitrogen as well as oxygen atoms are coordinated mutually in cis positions. The ipso-carbon atom is located trans to the lone pair of the central atom (Sb or Bi). All structures contain central MB2O3 ring system and the bonding situation within these rings is rather similar to the analogous heteroboroxines reported by us.11 Thus, M–O bond distances [in the range of 2.039(4)–2.053(3) Å for M = Sb, 2.161(3)– 2.169(3) Å for M = Bi] well correspond to the ∑cov(M, O) = 2.03 (Sb), 2.14 Å (Bi).20 The B–O bond distances [in the range of 1.325(6)–1.396(6) Å in 2a, 2b, 3a, 4a and 4b] are shorter than the ∑cov(B, O) = 1.48 Å.20 The O–M–O bonding angles are acute [in the range of 83.84(13)–86.21(11)°] and as a consequence the remaining internal M–O–B, B–O–B and O–B–O bonding angles are significantly wider than the ideal value for a six-membered ring (120°) [in the range of 123.4(4)–129.2(4)°]. In the majority of studied molecular structures, the central MB2O3 is essentially planar and the main deviation is seen in a slight bending of the antimony or bismuth atom from the mean B2O3 plane. The boron bonded pendant aromatic rings are nearly coplanar with this MB2O3 central core except for 3a. The steric repulsion between two ortho bonded CF3 groups and the heteroboroxine core in 3a leads to nearly perpendicular orientation of these phenyl rings. In turn, this rotation of the aromatic rings results in significant distortion of the central heteroboroxine core, this phenomenon is clearly evident from the comparison between molecular structures of 2a and 3a (Fig. 5). Noteworthy, any possible steric repulsion between CF3 groups in 2a is relaxed by their opposite positions in the structure.

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Table 1

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Selected bond lengths [Å] of studied compounds and schematic view on their structures

Bond lengths [Å]

2aa 2ba 3a 4a 4b 9a 9ca 10a 12c a

a

b

c

d

e

f

g

h

2.659(5) 2.677(4) 2.670(4) 2.677(4) 2.569(4) 2.637(4) 2.678(3) 2.631(2) 2.731(7) 2.566(6) 2.647(2) 2.680(2)

2.631(5) 2.619(5) 2.692(4) 2.704(4) 2.637(3) 2.637(4) 2.678(3) 2.614(2) 2.543(6) 2.668(6) 2.637(2) 2.759(2)

2.045(4) 2.046(3) 2.164(4) 2.161(3) 2.040(3) 2.053(3) 2.173(2) 2.0498(19) 2.045(5) 2.048(5) 2.057(2) 2.0306(15)

1.338(7) 1.329(6) 1.333(6) 1.327(6) 1.325(6) 1.335(6) 1.331(4) 1.330(4) 1.344(6) 1.332(9) 1.339(4) 1.341(3)

1.382(8) 1.381(7) 1.396(6) 1.393(6) 1.385(6) 1.382(5) 1.385(4) 1.383(4) 1.369(9) 1.371(9) 1.390(4) 1.353(3)

1.391(7) 1.385(7) 1.391(7) 1.394(6) 1.387(5) 1.382(5) 1.385(4) 1.380(4) 1.382(9) 1.391(9) 1.389(4) 1.457(3)

1.338(7) 1.336(7) 1.329(6) 1.326(6) 1.328(5) 1.335(6) 1.331(4) 1.337(4) 1.309(9) 1.310(9) 1.337(4) 1.405(3)

2.045(4) 2.039(4) 2.166(3) 2.169(3) 2.051(3) 2.053(3) 2.173(2) 2.0548(19) 2.045(5) 2.057(5) 2.0396(19) 2.0014(15)

Two independent molecules in the unit cell.

Table 2

Selected bonding angles [°] of studied compounds and schematic view on their structures

Bonding angles [Å]

2a

a

2ba 3a 4a 4b 9a 9ca 10a 12c a

ab

cd

de

ef

fg

gh

hc

118.00(15) 117.79(14) 118.09(11) 117.42(11) 120.04(12) 118.53(12) 119.16(8) 117.95(7) 119.29(18) 118.28(19) 120.97(7) 116.91(6)

128.7(4) 129.0(3) 128.3(3) 128.3(3) 126.3(2) 128.8(3) 126.8(2) 129.43(18) 126.8(5) 126.8(5) 125.78(19) 125.33(15)

123.7(5) 124.3(5) 125.5(5) 125.7(5) 124.3(3) 123.4(4) 125.0(3) 124.2(3) 124.5(7) 125.0(7) 123.4(3) 126.8(2)

125.9(4) 125.2(4) 126.3(4) 126.7(4) 123.5(3) 126.7(4) 127.9(3) 125.9(2) 126.9(6) 125.9(6) 123.8(2) 126.76(19)

123.4(5) 124.2(5) 125.6(5) 125.2(4) 124.3(4) 123.4(4) 125.0(3) 124.6(3) 123.8(7) 124.8(7) 123.5(3) 119.67(19)

129.2(4) 129.0(4) 127.9(4) 128.3(3) 128.3(3) 128.8(3) 126.8(2) 128.88(18) 128.7(5) 127.7(5) 126.19(19) 124.57(14)

85.54(16) 85.56(16) 83.84(13) 83.90(13) 84.64(11) 86.21(11) 84.43(8) 86.04(8) 87.6(2) 87.7(5) 84.76(8) 91.01(6)

Two independent molecules in the unit cell.

Closer inspection of crystal structures of 2a and 2b revealed contacts between two neighbouring molecules by a strong alignment of the heteroboroxine rings (Fig. 6). This interaction is mediated by four B–O and two M–O contacts. The B–O distances 3.275 Å in 2a and 3.095 Å in 2b (mean values) as well as M–O distances 3.741 Å in 2a and 3.569 Å in 2b are rather long and indicate only weak interactions. The metal atom is slightly

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bent out of the plane defined by remaining boron and oxygen atoms. The distance between these planes amounts 3.262 Å in 2a and 3.100 Å in 2b. Noteworthy, similar interaction was not observed in the case of structurally characterized tin heteroboroxines in this work nor in previously published examples.11 This fact may be most probably ascribed to the presence of the phenyl substituent on the tin atom that is pointed in the direc-

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Scheme 3

Fig. 5 View on the central core of 2a and 3a. Ligand L and hydrogen atoms were omitted for clarity.

Preparation of 12a–12c.

observed in 2a and 2b, for example these values are 3.462 to 3.410 Å (temperature dependent) in the case of (EtO)3B3O3.21a N-donor functionality containing heteroboroxines

Fig. 6 Intermolecular contacts between two heteroboroxine rings observed in 2b (analogous contacts were found in 2a and 9c).

tion of this interaction and thus hinders it by a steric repulsion. The nature of B–O contacts in 2a and 2b may be described as formation of Lewis pairs, when the occupied oxygen p orbitals donate electron density into the empty p boron orbitals. Similar intermolecular contacts were also observed and studied in classical boroxines R3B3O3.21 There are two types of interaction either between the boroxine core and one organic aromatic ring or directly between two B3O3 cores. In the latter case, the boron and oxygen atoms of both rings adopt nearly ideal eclipsed positions, while both heteroboroxine rings in 2a and 2b are a bit twisted (Fig. 6). This is most probably caused by the presence of metal atoms that also interact with one of the oxygen atoms and it is responsible for the distortion of the heteroboroxine rings. The intermolecular B–O contacts in classical boroxines are similar to those

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Compounds 9a–12c were prepared according to Schemes 1–3 in order to test any possibility of formation of intermolecular contacts mediated by the boron atoms and the nitrogen donor functionalities. All compounds 9a–12c were characterized by elemental analysis and 1H, 13C and 119Sn NMR spectroscopy (see the Experimental). Solution structures of 9a–12c are closely related to those observed for 1a–8c and before isolated heteroboroxines11 as judged from corresponding 1H, 13C and 119Sn NMR spectra. Thus, 1H NMR spectra confirmed the presence of the ligand L and organic residues of boronic acids in 1 : 2 ratio thereby corroborating the formation of six-membered heteroboroxine core. Furthermore, the observation of an AX pattern for methylene groups CH2N approved a pseudo-facial type coordination of the ligand L. The 119Sn NMR spectra of organotin(IV) compounds revealed one signal with expected chemical shifts −356.5 (11c) and −366.4 (12c).18 All these data suggest, that no intermolecular contacts are present in solution regardless which N-donor functionality was utilized in the structure of parent organoboronic acid. The molecular structures of 9a, 9c, 10a and 12c were determined in the solid state using single-crystal X-ray diffraction analysis and are depicted in Fig. 7–10, respectively. Molecular structures of 9a, 9c and 10a are closely related to those determined heteroboroxines 2a, 2b, 3a, 4a and 4b, thus, they are not described here in more detail and for relevant structural data see Tables 1 and 2. Noteworthy, 9a displays ring-ring contact similarly to that observed in 2a and 2b with the inter-plane distance being 3.196 Å. The B–O intermolecular contacts being 3.211 and 3.212 Å as well as the intermolecular Sb–O distance of 3.536 Å resemble the values observed in 2a. The closer inspection of the structure of 10a revealed the presence of intermolecular Sb–B contacts (Fig. 9) that are characterized by the distance Sb1–B2a of 3.869(3) Å. This value is only slightly shorter than the ∑vdW(Sb, B) = 4.00 Å22 indicating weak interaction, that may be most probably mediated by an interaction of the antimony lone pair with the empty boron p orbital. Similar weak intermolecular interactions involving the N,C,N-chelated antimony atom in a square pyramidal coordination environment have been recently observed in related

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Fig. 7 ORTEP plot of a molecule of 9a showing 30% probability displacement ellipsoid. Hydrogen atoms and the dichloromethane solvate molecule are omitted for clarity.

Fig. 10 ORTEP plot of a molecule of 12c (top) showing 30% probability displacement ellipsoid. Symmetry operator b = 1/2 − x, 1/2 + y, 1/2 − z. Hydrogen atoms and the benzene solvate molecule are omitted for clarity. The view on the polymeric chain formed via B–N contacts (bottom).

Fig. 8 ORTEP plot of a molecule of 9c showing 30% probability displacement ellipsoid. Hydrogen atoms and the dichloromethane solvate molecule are omitted for clarity.

Fig. 9 ORTEP plot of molecule of 10a showing 30% probability displacement ellipsoid and intermolecular Sb–B contacts. Symmetry operator a = 2 − x, −y, 1 − z. Hydrogen atoms except NH2 groups are omitted for clarity.

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trithiocarbonates LM(μ-S)2C(S) (M = Sb or Bi),23 but in this case the interaction between the Sb or Bi atoms and the carbon atom of the CS3 moiety was shown to be electrostatic. To the best of our knowledge, number of the structurally characterized antimony-boron complexes is rather low and include compounds X3B-Sb(SiMe3)3 (where X = Cl, Br, I), but in this case the Sb–B bond distances lie in the range 2.258–2.268 Å indicating rather strong dative connection.24 From this point of view, the Sb–B interaction observed in 10a may be considered as being on the border of bonding interaction. Nevertheless, no intermolecular B–N contact was observed in the structure of 9a, 9c and 10a, but this fact is not surprising as both aryl-bonded NH2 group as well as nitrile may be viewed as intrinsically weak donors. The situation is totally different in the case of the crystal structure of 12c. Compound 12c forms a polymeric chain via N→B dative connections in the solid state (Fig. 10), which is consistent with significantly better donating properties of pyridyl group. These contacts are mediated by one of the boron atoms (B2) from the boroxine core and one of flanking pyridyl functionalities (atom N4b) from an adjacent molecule. This interaction is characterized by the bond length B–N 1.699(3) Å that approaches ∑cov(B, N) = 1.56 Å20 and indicates strong intermolecular contact. This value is well comparable to those observed in classical 3-pyridyl substituted boroxine

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(3-Py)3B3O3 [the range of B–N 1.611–1.669 Å], but in this case two nitrogen atoms are involved in intermolecular N→B interactions leading to the formation of pentadecanuclear boron cage.25 The intermolecular N→B dative interactions present in 12c have of course significant influence on the central heteroboroxine core. While the uncoordinated boron atom B(1) retains its trigonal planar environment with sp2 hybridization, the coordination of the B(2) atom is tetrahedral. This fact also leads to slight distortion of the central heteroboroxine ring and the B(2)–O bonds [1.457(3) and 1.405(3) Å] are a little bit elongated in comparison with the B(1)–O bonds [1.341(3) and 1.353(3) Å]. To the best of our knowledge, 12c represents the first example of boroxine-based polymer incorporating a metal (tin) atom within its covalent framework. Importantly, dissolution of the crystals of 12c resulted in the polymer collapse back to monomeric units. Unfortunately, all attempts to grow single-crystals of antimony and bismuth congeners 12a and 12b failed and resulted only in polycrystalline material. Nevertheless, formation of similar coordination polymers seems to be probable and will be studied in the future.

Conclusions To summarize, we have developed a general path for preparation of stiba-, stanna- and bismaheteroboroxines with high tolerance to functional groups in boronic acid residues, but it turned out that the position of a functional group on the phenyl ring of the parent boronic acid (o- vs. m- vs. p-) is a crucial factor. Particularly in the case of antimony and bismuth compounds, the utilization of ortho substituted boronic acids did not lead to the desired heteroboroxines. Furthermore, it was shown that the heteroboroxines, analogously to classical boroxines, may participate in various intermolecular interactions. Thus, MB2O3 rings (M = Sb or Bi) in 2a, 2b and 9a are connected via B–O contacts forming weakly bonded dimeric units. The intermolecular N→B contacts in 12c allowed isolation of an unprecedented metal containing boroxine-based polymer in the solid state. It is believed, that modification of the heteroboroxine rings (i.e. increasing of inherent Lewis acidity of boron atoms and using of external N-donor molecules or utilization of other nitrogen donor containing boronic acids) will result in formation of similar metalcontaining boroxines-based poly(oligo)mers. The investigation targeting the reactivity of pendant functional groups on the periphery of heteroboroxine ring is another issue, which is now addressed in our group.

Experimental General remarks All air and moisture sensitive manipulations were carried out under an argon atmosphere using standard Schlenk tube techniques. All solvents were dried using Pure Solv-Innovative Technology equipment. The starting compounds The starting compounds (LSbO)2,15 (LBiO)2,16 L(Ph)Sn(CO3)17 and 1a–c11

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were prepared according to literature procedures. All boronic acids were obtained from the commercial suppliers and used as delivered. 1H, 13C, 19F and 119Sn NMR spectra were recorded on Bruker Avance 500 MHz spectrometer or Bruker Ultrashield 400 MHz, using 5 mm tuneable broad-band probe. Appropriate chemical shifts in 1H and 13C NMR spectra were related to the residual signals of the solvent (CDCl3: δ(1H) = 7.27 ppm and δ(13C) = 77.23 ppm) or to the external Me4Sn δ(119Sn) = 0.00 ppm in the case of the 119Sn NMR spectra. Elemental analyses were performed on an LECO-CHNS-932 analyzer.

Syntheses General procedure for the Sb and Bi compounds The mixture of the starting compound ((LSbO)2 or (LBiO)2) with four molar equivalents of respective boronic acid was dissolved in dichloromethane (30 mL) at room temperature. The resulting solution (in some cases the opalescent mixture) was stirred for additional 3–5 hours. Then the reaction mixture was filtered, if necessary, and the solution was evaporated in vacuo. Thus obtained solid was washed with hexane (10 mL) and dried in vacuo giving white solids, which were analysed as pure compounds by NMR spectroscopy. In some cases, additional recrystallization from dichloromethane–hexane mixture was necessary to obtain analytically pure sample (this is mentioned for respective compounds below). General procedure for the Sn compounds The mixture of the starting carbonate L(Ph)Sn(CO3) with two molar equivalents of respective boronic acid was dissolved in dichloromethane (30 mL) at room temperature. The resulting solution (in some cases the opalescent mixture) was stirred 24 hours. Then the solution was evaporated in vacuo. Thus obtained solid was washed with hexane (10 mL) and dried in vacuo giving white solids, which were analysed as pure compounds by NMR spectroscopy. In the case of 9c and 12c, single crystalline material suitable for X ray diffraction analysis were grown by slow evaporation of saturated toluene solutions. Synthesis of 2a. Following the general procedure: (LSbO)2 (139 mg, 0.21 mmol) and 3-CF3C6H4B(OH)2 (145 mg, 0.76 mmol) in dichloromethane (30 mL) gave 2a as white crystalline solid. Yield: 228 mg, 87%. M.p. 186–190 °C. Anal. calcd for C26H27B2F6N2O3Sb (MW 672.88): C, 46.4; H, 4.0; Found: C, 46.8; H, 4.2%. 1H NMR (500 MHz, CDCl3): δ 2.13 (6H, s(br), (CH3)2N), 2.86 (6H, s(br), (CH3)2N), 3.91 (4H, AX pattern, 2JH–H = 13.5 Hz, (CH2)N), 7.06 (2H, d, L-H3,5), 7.20 (1H, t, L-H4), 7.52 (2H, dd, Ar-H), 7.67 (2H, d, Ar-H), 8.18 (2H, d, Ar-H), 8.28 (2H, s, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.5 (s, (CH3)2N), 45.2 (s, (CH3)2N), 63.2 (s, (CH2)N), 124.9 (q, 1JF–C = 272.2 Hz, CF3), 126.5 (s, Ar-C), 126.7 (q, 3JF–C = 3.7 Hz, Ar-C), 128.0 (s, L-C3,5), 129.6 (s, L-C4), 129.8 (q, 2JF–C = 31.6 Hz, Ar-C), 131.3 (q, 3JF–C = 3.8 Hz, Ar-C), 138.1 (s, Ar-C), 147.3 (s, L-C2,6), 155.1 (s, L-C1), (Ar-C1-B) not observed. 19 F NMR (376.50 MHz, CDCl3): δ −62.5 (CF3). Synthesis of 2b. Following the general procedure: (LBiO)2 (117 mg, 0.14 mmol) and 3-CF3C6H4B(OH)2 (97 mg,

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0.51 mmol) in dichloromethane (30 mL) gave 2b as white crystalline solid. Yield: 176 mg, 91%. M.p. 169–173 °C. Anal. calcd for C26H27BiB2F6N2O3 (MW 760.11): C, 41.1; H, 3.6; Found: C, 41.3; H, 3.9%. 1H NMR (500 MHz, CDCl3): δ 2.16 (6H, s, (CH3)2N), 2.93 (6H, s, (CH3)2N), 4.02 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.29 (1H, t, L-H4), 7.47 (4H, m, L-H3,5 and Ar-H), 7.62 (2H, d, Ar-H), 8.16 (2H, d, Ar-H), 8.28 (2H, s, Ar-H). 13 C{1H} NMR (100.61 MHz, CDCl3): δ 42.5 (s, (CH3)2N), 46.0 (s, (CH3)2N), 65.6 (s, (CH2)N), 125.0 (q, 1JF–C = 272.2 Hz, CF3), 126.2 (q, 3JF–C = 4.0 Hz, Ar-C), 127.8 (s, Ar-C), 128.6 (s, L-C3,5), 129.6 (s, L-C4), 129.6 (q, 2JF–C = 32.2 Hz, Ar-C), 131.4 (q, 3JF–C = 3.8 Hz, Ar-C), 138.2 (s, Ar-C), 152.2 (s, L-C2,6), 205.5 (s, L-C1), (Ar-C1-B) not observed. 19F NMR (376.50 MHz, CDCl3): δ −62.4 (CF3). Synthesis of 2c. Following the general procedure: L(Ph)Sn(CO3) (91 mg, 0.20 mmol) and 3-CF3C6H4B(OH)2 (78 mg, 0.40 mmol) in dichloromethane (30 mL) gave 2c as white crystalline solid. Yield: 119 mg, 78%. M.p. 138–140 °C. Anal. calcd for C32H32B2F6N2O3Sn (MW 746.64): C, 51.4; H, 4.1; Found: C, 51.5; H, 4.3%. 1H NMR (500 MHz, CDCl3): δ 2.41 (12H, s, (CH3)2N), 3.88 (4H, AX pattern, 2JH–H = 12.0 Hz, (CH2)N), 7.12 (2H, d, L-H3,5), 7.32 (1H, t, L-H4), 7.50 (3H, m, Ar-H), 7.60 (2H, dd, Ar-H), 7.75 (2H, d, Ar-H), 7.81 (2H, d, Ar-H), 8.37 (2H, d, Ar-H), 8.48 (2H, s, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.1 (s, (CH3)2N), 63.0 (s, (CH2)N), 124.9 (q, 1JF–C = 272.7 Hz, CF3), 126.4 (q, 3JF–C = 4.0 Hz, Ar-C), 127.4 (s, Ar-C), 127.9 (s, L-C3,5), 128.8 (s, Ph-C3,5), 129.9 (q, 2JF–C = 31.2 Hz, Ar-C), 129.9 (s, Ph-C4), 130.4 (s, L-C4), 131.4 (q, 3JF–C = 4.0 Hz, Ar-C), 134.5 (s, Ph-C2,6), 138.2 (s, Ar-C), 138.9 (s, Ph-C1), 139.0 (s(br), Ar-C1-B), 141.4 (s, L-C1), 145.0 (s, L-C2,6). 19F NMR (376.50 MHz, CDCl3): δ −62.5 (CF3). 119Sn NMR (MHz, CDCl3): δ −363.8. Synthesis of 3a. Following the general procedure: (LSbO)2 (153 mg, 0.23 mmol) and 2-CF3C6H4B(OH)2 (160 mg, 0.84 mmol) in dichloromethane (30 mL) gave 3a as white crystalline solid (yield 214 mg, 75%), M.p. 166–168 °C. Anal. calcd for C26H27B2F6N2O3Sb (MW 672.88): C, 46.4; H, 4.0; Found: C, 46.7; H, 4.3%. 1H NMR (500 MHz, CDCl3): δ 2.04 (6H, s(br), (CH3)2N), 2.53 (6H, s(br), (CH3)2N), 3.71 (4H, AX pattern, 2JH–H = 13.6 Hz, (CH2)N), 7.09 (2H, d, Ar-H), 7.27 (1H, t, L-H4), 7.34 (2H, m, L-H3,5), 7.41 (2H, dd, Ar-H), 7.56 (4H, m, Ar-H). 13C {1H} NMR (100.61 MHz, CDCl3): δ 42.1 (s, (CH3)2N), 45.2 (s, (CH3)2N), 63.1 (s, (CH2)N), 125.0 (q, 3JF–C = 4.7 Hz, Ar-C), 125.2 (q, 1JF–C = 273.3 Hz, CF3), 126.1 (s, Ar-C), 127.7 (s, L-C3,5), 129.5 (s, L-C4), 130.6 (s, Ar-C), 132.0 (q, 2JF–C = 30.8 Hz, Ar-C), 132.8 (s, Ar-C), 138.5 (s(br), Ar-C) 147.3 (s, L-C2,6), 154.8 (s, L-C1). 19F NMR (376.50 MHz, CDCl3): δ −59.4 (CF3). Synthesis of 3b. Following the general procedure: (LBiO)2 (96 mg, 0.12 mmol) and 2-CF3C6H4B(OH)2 (88 mg, 0.46 mmol) in dichloromethane (30 mL) gave 3b, after additional recrystallization, as white crystalline solid (yield 58 mg, 33%), M.p. 95–97 °C. Anal. calcd for C26H27BiB2F6N2O3 (MW 760.11): C, 41.1; H, 3.6; Found: C, 41.4; H, 3.7%. 1H NMR (500 MHz, CDCl3): δ 2.08 (6H, s(br), (CH3)2N), 2.65 (6H, s(br), (CH3)2N), 3.90 (4H, AX pattern, 2JH–H = 13.5 Hz, (CH2)N), 7.31–7.42 (5H, m, L-H3,4,5 and Ar-H), 7.47 (2H, d, Ar-H), 7.54 (2H, d, Ar-H),

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7.58 (2H, s, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.3 (s, (CH3)2N), 45.9 (s, (CH3)2N), 65.5(s, (CH2)N), 124.8 (q, 3JF–C = 4.6 Hz, Ar-C), 125.3 (q, 1JF–C = 273.9 Hz, CF3), 127.3 (s, Ar-C), 128.3 (s, L-C3,5), 128.9 (s, L-C4), 130.6 (s, Ar-C), 132.0 (q, 2 JF–C = 30.4 Hz, Ar-C), 133.2 (s, Ar-C), 152.4 (s, L-C2,6), 205.7 (s, L-C1) (Ar-C1-B) not observed. 19F NMR (376.50 MHz, CDCl3): δ −59.6 (CF3). Synthesis of 3c. Following the general procedure: L(Ph)Sn(CO3) (153 mg, 0.34 mmol) and 2-CF3C6H4B(OH)2 (130 mg, 0.68 mmol) in dichloromethane (30 mL) gave 3c as white crystalline solid. Yield: 225 mg, 88%. M.p. 119–122 °C. Anal. calcd for C32H32B2F6N2O3Sn (MW 746.64): C, 50.6; H, 3.8; Found: C, 50.8; H, 4.0%. 1H NMR (500 MHz, CDCl3): δ 2.13 (12H, s, (CH3)2N), 3.69 (4H, AX pattern, 2JH–H = 16.0 Hz, (CH2)N), 7.11 (2H, d, L-H3,5), 7.32–7.53 (8H, m, L-H4 and Ar-H), 7.68 (2H, d, Ar-H), 7.76 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.5 (s, (CH3)2N), 62.7 (s, (CH2)N), 125.2 (q, 1JF–C = 271.7 Hz, CF3), 124.7 (q, 3JF–C = 5.0 Hz, Ar-C), 127.2 (s, Ph-C3,5), 127.4 (s, Ar-C), 128.3 (s, L-C3,5), 128.5 (s, Ar-C), 129.6 (s, Ph-C4), 130.2 (s, L-C4), 130.4 (s, Ar-C), 133.1 (s, Ar-C), 131.9 (q, 2JF–C = 31.6 Hz, Ar-C), 134.5 (s, Ph-C2,6), 138.6 (s, Ph-C1), 139.1(Ar-C1-B), 141.8 (s, L-C1), 145.2 (s, L-C2,6). 19F NMR (376.50 MHz, CDCl3): δ −59.1 (CF3). 119Sn NMR (MHz, CDCl3): δ −369.2. Synthesis of 4a. Following the general procedure: (LSbO)2 (139 mg, 0.21 mmol) and 4-BrC6H4B(OH)2 (156 mg, 0.78 mmol) in dichloromethane (30 mL) gave 4a as white crystalline solid. Yield: 235 mg, 87%. M.p. 201–206 °C. Anal. calcd for C24H27B2Br2N2O3Sb (MW 694.67): C, 41.5; H, 3.9; Found: C, 41.8; H, 4.1%. 1H NMR (500 MHz, CDCl3): δ 2.10 (6H, s(br), (CH3)2N), 2.83 (6H, s(br), (CH3)2N), 3.89 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.05 (2H, d, L-H3,5), 7.19 (1H, t, L-H4), 7.52 (4H, d, Ar-H), 7.86 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.3 (s(br), (CH3)2N), 45.7 (s(br), (CH3)2N), 63.2 (s, (CH2)N), 124.9 (s, Ar-CBr), 126.4 (s, L-C3,5), 129.5 (s, L-C4), 130.8 (Ar-C), 136.5 (s, Ar-C), 147.2 (s, L-C2,6), 155.2 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 4b. Following the general procedure: (LBiO)2 (116 mg, 0.14 mmol) and 4-BrC6H4B(OH)2 (101 mg, 0.50 mmol) in dichloromethane (30 mL) gave 4b as white crystalline solid. Yield: 175 mg, 90%. M.p. 183–187 °C. Anal. calcd for C24H27B2BiBr2N2O3 (MW 781.90): C, 36.9; H, 3.5; Found: C, 37.2; H, 3.6%. 1H NMR (500 MHz, CDCl3): δ 2.15 (6H, s, (CH3)2N), 2.90 (6H, s, (CH3)2N), 4.00 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.27 (1H, t, L-H4), 7.41 (2H, d, L-H3,5), 7.49 (4H, d, Ar-H), 7.85 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.4 (s(br), (CH3)2N), 46.2 (s(br), (CH3)2N), 65.6 (s, (CH2)N), 124.4 (s, Ar-CBr), 128.6 (s, L-C3,5), 129.0 (s, L-C4), 130.7 (Ar-C), 136.7 (s, Ar-C), 152.1 (s, L-C2,6), 205.2 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 4c. Following the general procedure: L(Ph)Sn(CO3) (176 mg, 0.39 mmol) and 4-BrC6H4B(OH)2 (158 mg, 0.78 mmol) in dichloromethane (30 mL) gave 4c as white crystalline solid. Yield: 259 mg, 86%. M.p. 169–172 °C. Anal. calcd for C30H32B2Br2N2O3Sn (MW 768.72): C, 46.7; H, 4.0; Found: C, 46.9; H, 4.2%. 1H NMR (500 MHz, CDCl3): δ 2.13 (12H, s (br), (CH3)2N), 3.56 (4H, AX pattern, 2JH–H = 12.8 Hz, (CH2)N),

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6.84 (2H, d, L-H3,5), 7.05 (1H, t, L-H4), 7.18 (3H, m, Ar-H), 7.26 (4H, d, Ar-H), 7.46 (2H, d, Ar-H), 7.66 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.7 (s(br), (CH3)2N), 63.2 (s, (CH2)N), 124.5 (s, Ar-CBr), 127.3 (s, Ph-C3,5), 128.7 (s, L-C3,5), 129.7 (s, Ph-C4), 130.2 (s, L-C4), 130.5 (Ar-C), 134.7 (s, PhC2,6), 136.5 (s, Ar-C), 139.1 (s, Ph-C1), 141.5 (s, L-C1), 145.1 (s, L-C2,6), (Ar-C1-B) not observed. 119Sn NMR (MHz, CDCl3): δ −361.4. Synthesis of 5a. Following the general procedure: (LSbO)2 (113 mg, 0.17 mmol) and 3-BrC6H4B(OH)2 (125 mg, 0.62 mmol) in dichloromethane (30 mL) gave 5a as white crystalline solid. Yield: 158 mg, 73%. M.p. 148–151 °C. Anal. calcd for C24H27B2Br2N2O3Sb (MW 694.67): C, 41.5; H, 3.9; Found: C, 41.7; H, 4.3%. 1H NMR (500 MHz, CDCl3): δ 2.11 (6H, s(br), (CH3)2N), 2.82 (6H, s(br), (CH3)2N), 3.89 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.06 (2H, d, L-H3,5), 7.20 (1H, t, L-H4), 7.27 (2H, dd, Ar-H), 7.53 (2H, d, Ar-H), 7.90 (2H, d, Ar-H), 8.10 (2H, s, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 63.2 (s, (CH2)N), 122.6 (s, Ar-CBr), 126.4 (s, L-C3,5), 129.5 (Ar-C), 129.6 (s, L-C4), 133.0 (s, Ar-C), 133.2 (s, Ar-C), 137.7 (s, Ar-C), 147.3 (s, L-C2,6), 155.1 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 5b. Following the general procedure: (LBiO)2 (116 mg, 0.14 mmol) and 3-BrC6H4B(OH)2 (102 mg, 0.51 mmol) in dichloromethane (30 mL) gave 5b as white crystalline solid. Yield: 168 mg, 85%. M.p. 153–156 °C. Anal. calcd for C24H27B2BiBr2N2O3 (MW 781.90): C, 36.9; H, 3.5; Found: C, 37.1; H, 3.2%. 1H NMR (500 MHz, CDCl3): δ 2.15 (6H, s(br), (CH3)2N), 2.91 (6H, s(br), (CH3)2N), 4.02 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.28 (3H, m, L-H3,4,5), 7.43 (2H, dd, Ar-H), 7.51 (2H, d, Ar-H), 7.92 (2H, d, Ar-H), 8.12 (2H, s, Ar-H). 13C {1H} NMR (100.61 MHz, CDCl3): δ 42.4 (s, (CH3)2N), 46.1 (s, (CH3)2N), 65.6 (s, (CH2)N), 122.5 (s, Ar-CBr), 128.6 (s, L-C3,5), 129.0 (s, L-C4), 129.4 (Ar-C), 132.5 (s, Ar-C), 133.4 (s, Ar-C), 137.8 (s, Ar-C), 152.1 (s, L-C2,6), 205.4 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 5c. Following the general procedure: L(Ph)Sn(CO3) (92 mg, 0.21 mmol) and 3-BrC6H4B(OH)2 (83 mg, 0.42 mmol) in dichloromethane (30 mL) gave 5c as white crystalline solid. Yield: 119 mg, 75%. M.p. 106–108 °C. Anal. calcd for C30H32B2Br2N2O3Sn (MW 768.72): C, 46.1; H, 3.9; Found: C, 46.3; H, 4.1%. 1H NMR (500 MHz, CDCl3): δ 2.41 (12H, s (br), (CH3)2N), 3.88 (4H, AX pattern, 2JH–H = 12.0 Hz, (CH2)N), 7.15 (2H, d, L-H3,5), 7.36 (4H, m, L-H4 and Ar-H), 7.51 (2H, dd, Ar-H), 7.63 (2H, dd, Ar-H), 7.79 (2H, dd, Ar-H), 8.07 (2H, s, ArH), 8.27 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 63.3 (s, (CH2)N), 122.7 (s, Ar-CBr), 127.3 (s, L-C3,5), 128.4 (s, Ar-C), 128.9 (s, Ph-C3,5), 129.4 (Ar-C), 129.9 (s, Ph-C4), 130.4 (s, L-C4), 132.7 (s, Ar-C), 133.4 (s, Ar-C), 134.7 (s, Ph-C2,6), 137.9 (s, Ar-C), 139.9 (s, Ph-C1), 141.7 (s, L-C1), 145.2 (s, L-C2,6), (Ar-C1-B) not observed. 119Sn NMR (MHz, CDCl3): δ −362.9. Synthesis of 6c. Following the general procedure: L(Ph)Sn(CO3) (90 mg, 0.20 mmol) and 2-BrC6H4B(OH)2 (81 mg, 0.40 mmol) in dichloromethane (30 mL) gave 6c as white crys-

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talline solid. Yield: 121 mg, 78%. M.p. 112–114 °C. Anal. calcd for C30H32B2Br2N2O3Sn (MW 768.72): C, 46.3; H, 4.0; Found: C, 46.5; H, 4.3%. 1H NMR (500 MHz, CDCl3): δ 2.36 (12H, s (br), (CH3)2N), 3.95 (4H, AX pattern, 2JH–H = 12.0 Hz, (CH2)N), 7.23 (2H, d, L-H3,5), 7.36 (2H, dd, Ar-H), 7.47 (1H, t, L-H4), 7.58 (7H, m, Ar-H), 7.86 (2H, d, Ar-H), 7.91 (2H, d, Ar-H). 13C {1H} NMR (100.61 MHz, CDCl3): δ 44.9 (s, (CH3)2N), 63.1 (s, (CH2)N), 126.2 (s, Ar-CBr), 127.1 (s, Ar-C), 127.3 (s, Ph-C3,5), 129.5 (Ar-C), 128.7 (s, L-C3,5), 129.7 (s, Ph-C4), 129.8 (s, Ar-C), 130.4 (s, L-C4), 132.3 (s, Ar-C), 134.7 (s, Ph-C2,6), 135.9 (s, Ar-C), 139.0 (s, Ph-C1), 141.3 (Ar-C1-B), 142.2 (s, L-C1), 145.5 (s, L-C2,6). 119Sn NMR (MHz, CDCl3): δ −364.9. Synthesis of 7c. Following the general procedure: L(Ph)Sn (CO3) (81 mg, 0.18 mmol) and 2-OCH3C6H4B(OH)2 (55 mg, 0.36 mmol) in dichloromethane (30 mL) gave 7c as white crystalline solid. Yield: 87 mg, 72%. M.p. 105–107 °C. Anal. calcd for C32H38B2N2O5Sn (MW 670.98): C, 57.1; H, 5.5; Found: C, 57.3; H, 5.7%. 1H NMR (500 MHz, CDCl3): δ 2.52 (12H, s(br), (CH3)2N), 4.04 (6H, s, OCH3), 4.10 (4H, AX pattern, 2JH–H = 12.0 Hz, (CH2)N), 7.10 (2H, d, L-H3,5), 7.23 (2H, dd, Ar-H), 7.30 (2H, d, Ar-H), 7.58 (1H, t, L-H4), 7.65–7.63 (5H, m, Ar-H), 8.03 (2H, d, Ar-H), 8.33 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.6 (CH3)2N, 62.7 (s, (CH2)N), 110.3 (s, Ar-C), 120.1 (Ar-C), 127.2 (s, Ph-C3,5), 128.5 (s, L-C3,5), 129.5 (s, Ph-C4), 130.1 (s, L-C4), 133.0 (s, Ar-C), 130.7 (s, Ar-C), 137.7 (s, Ar-C), 134.9 (s, Ph-C2,6), 137.7 (s, Ar-C), 139.8 (s, Ph-C1), 142.5 (s, L-C1), 145.5 (s, L-C2,6), 164.4 (s, Ar-COCH3), (Ar-C1-B) not observed. 119Sn NMR (MHz, CDCl3): δ −360.1. Synthesis of 8c. Following the general procedure: L(Ph)Sn(CO3) (44 mg, 0.10 mmol) and 2-OHCC6H4B(OH)2 (30 mg, 0.20 mmol) in dichloromethane (30 mL) gave 8c as white crystalline solid. Yield: 47 mg, 68%. M.p. 209–210 °C. Anal. calcd for C34H38B2N2O5Sn (MW 695.00): C, 58.5; H, 5.2; Found: C, 58.8; H, 5.5%. 1H NMR (500 MHz, CDCl3): δ 2.35 (12H, s(br), (CH3)2N), 3.87 (4H, AX pattern, 2JH–H = 16.0 Hz, (CH2)N), 7.26 (2H, d, L-H3,5), 7.68–7.57 (8H, m, L-H4 and Ar-H), 7.92 (2H, d, Ar-H), 8.08 (4H, dd, Ar-H), 10.85 (2H, s, CHvO). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.7 (CH3)2N, 62.9 (s, (CH2)N), 125.3 (s, Ar-C), 126.8 (s, L-C3,5), 128.9 (s, L-C3,5), 129.9 (s, L-C4), 130.5 (s, Ph-C4), 132.8 (s, Ar-C), 134.3 (s, Ph-C2,6), 135.0 (s, Ar-C), 138.5 (s, Ph-C1), 140.7 (s, Ar-C), 141.6 (s, L-C1), 142.9 (Ar-C1-B), 144.9 (s, L-C2,6), 195.8 (s, Ar-CHO). 119Sn NMR (MHz, CDCl3): δ −368.9. Synthesis of 9a. Following the general procedure: (LSbO)2 (110 mg, 0.17 mmol) and 4-NCC6H4B(OH)2 (98 mg, 0.67 mmol) in dichloromethane (30 mL) gave 9a as white crystalline solid. Yield: 172 mg, 88%. M.p. 194–197 °C. Anal. calcd for C26H27B2N4O3Sb (MW 586.90): C, 53.2; H, 4.6; Found: C, 53.5; H, 4.9%. 1H NMR (500 MHz, CDCl3): δ 2.11 (6H, s(br), (CH3)2N), 2.84 (6H, s(br), (CH3)2N), 3.89 (4H, AX pattern, 2JH–H = 13.6 Hz, (CH2)N), 7.08 (2H, d, L-H3,5), 7.22 (1H, t, L-H4), 7.65 (4H, d, Ar-H), 8.04 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 63.1 (s, (CH2)N), 113.3 (s, CN), 119.7 (s, Ar-CCN), 126.5 (s, L-C3,5), 129.8 (s, L-C4), 131.2 (Ar-C), 135.1 (s, Ar-C), 147.2 (s, L-C2,6), 154.9 (s, L-C1), (Ar-C1-B) not observed.

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Synthesis of 9b. Following the general procedure: (LBiO)2 (101 mg, 0.12 mmol) and 4-NCC6H4B(OH)2 (70 mg, 0.48 mmol) in dichloromethane (30 mL) gave 9b as white crystalline solid. Yield: 142 mg, 87%. M.p. 168–171 °C. Anal. calcd for C26H27B2BiN4O3 (MW 674.13): C, 46.3; H, 4.0; Found: C, 46.1; H, 3.9%. 1H NMR (500 MHz, CDCl3): δ 2.10 (6H, s, (CH3)2N), 2.84 (6H, s, (CH3)2N), 3.96 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.32 (1H, t, L-H4), 7.45 (2H, d, L-H3,5), 7.64 (4H, d, Ar-H), 8.04 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.5 (s, (CH3)2N), 46.2 (s, (CH3)2N), 65.6 (s, (CH2)N), 112.9 (s, CN), 119.9 (s, Ar-CCN), 128.7 (s, L-C3,5), 129.2 (s, L-C4), 131.2 (Ar-C), 135.2 (s, Ar-C), 152.2 (s, L-C2,6), (L-C1) and (Ar-C1-B) not observed. Synthesis of 9c. Following the general procedure: L(Ph)Sn(CO3) (416 mg, 0.93 mmol) and 4-NCC6H4B(OH)2 (273 mg, 1.86 mmol) in dichloromethane (30 mL) gave 9c as white crystalline solid. Yield: 504 mg, 82%. M.p. 138–140 °C. Anal. calcd for C32H32B2N4O3Sn (MW 660.95): C, 58.0; H, 4.7; Found: C, 58.2; H, 4.9%. 1H NMR (500 MHz, CDCl3): δ 2.35 (12H, s(br), (CH3)2N), 3.89 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.15 (2H, d, L-H3,5), 7.33 (1H, t, L-H4), 7.46 (3H, m, Ar-H),7.69 (4H, d, Ar-H) 7.72 (2H, d, Ar-H) 8.10 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 63.2 (s, (CH2)N), 110.2 (s, Ar-C), 113.1 (s, CN), 119.8 (s, Ar-CCN), 127.4 (s, Ph-C3,5), 128.9 (s, L-C3,5), 130.1 (s, Ph-C4), 130.6 (s, L-C4), 131.0 (Ar-C), 134.6 (s, PhC2,6), 135.0 (s, Ar-C), 138.9 (s, Ph-C4), 141.3 (s, L-C1), 145.2 (s, L-C2,6), (Ar-C1-B) not observed. 119Sn NMR (MHz, CDCl3): δ −365.4. Synthesis of 10a. Following the general procedure: (LSbO)2 (96 mg, 0.15 mmol) and 3-NH2C6H4B(OH)2 (80 mg, 0.58 mmol) in dichloromethane (30 mL) gave 10a as white crystalline solid. Yield: 126 mg, 76%. M.p. 191–193 °C. Anal. calcd for C24H31B2N4O3Sb (MW 566.91): C, 50.9; H, 5.5; Found: C, 51.1; H, 5.7%. 1H NMR (500 MHz, CDCl3): δ 2.20 (6H, s(br), (CH3)2N), 2.76 (6H, s(br), (CH3)2N), 3.63 (4H, s, NH2), 3.89 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 6.76 (2H, dd, Ar-H), 7.01 (2H, d, L-H3,5), 7.16 (3H, m, L-H4, and Ar-H), 7.36 (2H, d, Ar-H), 7.43 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 63.3 (s, (CH2)N), 117.0 (s, Ar-C), 121.8 (Ar-C), 125.5 (Ar-C), 126.3 (s, L-C3,5), 128.4 (Ar-C), 129.2 (s, L-C4), 145.6 (Ar-CNH2), 147.3 (s, L-C2,6), 155.4 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 10b. Following the general procedure: (LBiO)2 (67 mg, 0.081 mmol) and 3-NH2C6H4B(OH)2 (44 mg, 0.32 mmol) in dichloromethane (30 mL) gave 10b as white crystalline solid. Yield: 96 mg, 91%. M.p. 170–175 °C. Anal. calcd for C24H31B2BiN4O3 (MW 654.14): C, 44.1; H, 4.8; Found: C, 43.8; H, 5.1%. 1H NMR (500 MHz, CDCl3): δ 2.13 (6H, s(br), (CH3)2N), 2.90 (6H, s(br), (CH3)2N), 3.62 (4H, s, NH2), 3.00 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 6.74 (2H, dd, Ar-H), 7.18 (2H, dd, L-H3,5), 7.24 (1H, t, L-H4), 7.37 (4H, m, Ar-H), 7.44 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.4 (s, (CH3)2N), 46.2 (s, (CH3)2N), 65.6 (s, (CH2)N), 116.7 (s, Ar-C), 122.0 (Ar-C), 125.7 (Ar-C), 128.3 (s, L-C3,5), 128.5 (Ar-C), 128.6

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(s, L-C4), 145.6 (Ar-CNH2), 152.0 (s, L-C2,6), 205.0 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 10c. Following the general procedure: L(Ph)Sn(CO3) (149 mg, 0.33 mmol) and 3-NH2C6H4B(OH)2 (103 mg, 0.66 mmol) in dichloromethane (30 mL) gave 10c as white crystalline solid. Yield: 192 mg, 90%. M.p. 144–150 °C. Anal. calcd for C30H36B2N4O3Sn (MW 640.96): C, 55.9; H, 5.5; Found: C, 56.2; H, 5.7%. 1H NMR (500 MHz, CDCl3): δ 2.29 (12H, s (br), (CH3)2N), 3.58 (4H, s, NH2), 3.77 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 6.70 (2H, d, Ar-H), 7.02 (2H, d, L-H3,5), 7.13 (5H, dd, Ar-H), 7.23 (1H, t, L-H4), 7.35 (2H, d, Ar-H), 7.43 (2H, d, Ar-H) 7.66 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.8 (s, (CH3)2N), 63.2 (s, (CH2)N), 116.7 (s, Ar-C), 121.9 (Ar-C), 125.5 (Ar-C), 127.2 (s, Ph-C3,5), 128.3 (s, L-C3,5), 128.5 (Ar-C), 129.5 (s, Ph-C4), 130.0 (s, L-C4), 134.6 (s, Ph-C2,6), 139.4 (s, Ph-C1), 141.9 (s, L-C1), 145.2 (s, L-C2,6), 145.4 (Ar-CNH2), (Ar-C1-B) not observed. 119Sn NMR (MHz, CDCl3): δ −357.9. Synthesis of 11a. Following the general procedure: (LSbO)2 (99 mg, 0.15 mmol) and 3-NMe2C6H4B(OH)2 (99 mg, 0.15 mmol) in dichloromethane (30 mL) gave 11a as white crystalline solid. Yield: 157 mg, 84%. M.p. 183–186 °C. Anal. calcd for C28H39B2N4O3Sb (MW 623.02): C, 54.0; H, 6.3; Found: C, 54.2; H, 6.0%. 1H NMR (500 MHz, CDCl3): δ 2.15 (6H, s(br), (CH3)2N), 2.80 (6H, s(br), (CH3)2N), 2.98 (12H, s, N(CH3)2), 3.91 (4H, AX pattern, 2JH–H = 13.6 Hz, (CH2)N), 6.86 (2H, dd, Ar-H), 7.00 (2H, d, L-H3,5), 7.15 (1H, t, L), 7.27 (2H, dd, Ar-H), 7.44 (2H, d, Ar-H), 7.55 (2H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ signals of (CH3)2N not observed due to the strong broadening, 41.1 (s, (CH3)2N-Ar), 63.3 (s, (CH2)N), 114.9 (s, Ar-C), 119.7 (Ar-C), 123.8 (Ar-C), 126.3 (s, L-C3,5), 128.3 (Ar-C), 129.1 (s, L-C4), 147.2 (s, L-C2,6), 150.2 (Ar-CNMe2), 155.5 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 11b. Following the general procedure: (LBiO)2 (99 mg, 0.12 mmol) and 3-NMe2C6H4B(OH)2 (78 mg, 0.48 mmol) in dichloromethane (30 mL) gave 11b as white crystalline solid. Yield: 109 mg, 63%. M.p. 143–147 °C. Anal. calcd for C28H39B2BiN4O3 (MW 710.25): C, 47.4; H, 5.5; Found: C, 47.6; H, 5.8%. 1H NMR (500 MHz, CDCl3): δ 2.13 (6H, s(br), (CH3)2N), 2.93 (6H, s(br), (CH3)2N), 3.00 (12H, s, N(CH3)2), 4.02 (4H, AX pattern, 2JH–H = 13.4 Hz, (CH2)N), 6.85 (2H, dd, Ar-H), 7.23 (1H, t, L), 7.30 (2H, d, L-H3,5), 7.35 (2H, d, Ar-H), 7.47 (2H, d, Ar-H), 7.59 (2H, d, Ar-H).13C{1H} NMR (100.61 MHz, CDCl3): δ 41.4 (s, (CH3)2N-Ar), 42.4 (s, (CH3)2N), 46.1 (s, (CH3)2N), 65.6 (s, (CH2)N), 114.6 (s, Ar-C), 120.0 (Ar-C), 124.1 (Ar-C), 128.1 (s, L-C3,5), 128.4 (Ar-C), 128.5 (s, L-C4), 150.2 (Ar-CNMe2), 151.9 (s, L-C2,6), 205.0 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 11c. Following the general procedure: L(Ph)Sn(CO3) (158 mg, 0.35 mmol) and 3-NMe2C6H4B(OH)2 (116 mg, 0.70 mmol) in dichloromethane (30 mL) gave 11c as blue crystalline solid. Yield: 170 mg, 69%. M.p. 114–116 °C. Anal. calcd for C34H44B2N4O3Sn (MW 697.07): C, 58.3; H, 6.2; Found: C, 58.6; H, 6.4%. 1H NMR (500 MHz, CDCl3): δ 2.57 (12H, s(br), (CH3)2N), 3.20 (12H, s, N(CH3)2), 4.06 (4H, AX pattern, 2JH–H = 16.1 Hz, (CH2)N), 7.08 (2H, d, Ar-H), 7.26 (2H, d, L-H3,5), 7.48 (1H, t, L-H4), 7.52 (3H, m, Ar-H), 7.61 (2H, d, Ar-H), 7.73 (2H,

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d, Ar-H), 7.86 (2H, d, Ar-H), 7.96 (2H, d, Ar-H).13C{1H} NMR (100.61 MHz, CDCl3): δ 41.1 (s, (CH3)2N), 44.8 (s, (CH3)2N-Ar), 63.2 (s, (CH2)N), 114.8 (s, Ar-C), 119.9 (Ar-C), 124.0 (Ar-C), 127.3 (s, Ph-C3,5), 128.2 (s, L-C3,5), 128.6 (Ar-C), 129.6 (s, PhC4), 130.1 (s, L-C4), 134.8 (s, Ph-C2,6), 138.9 (s(br), Ar-C1-B), 139.5 (s, Ph-C1), 142.1 (s, L-C1), 145.3 (s, L-C2,6), 150.2 (Ar-CNMe2). 119Sn NMR (MHz, CDCl3): δ −356.5. Synthesis of 12a. Following the general procedure: (LSbO)2 (108 mg, 0.16 mmol) and 4-PyB(OH)2 (80 mg, 0.65 mmol) in dichloromethane (30 mL) gave 12a as cream crystalline solid. Yield: 159 mg, 90%. M.p. 117 °C-dec. Anal. calcd for C22H27B2N4O3Sb (MW 538.86): C, 49.0; H, 5.1; Found: C, 49.1; H, 5.3%. 1H NMR (500 MHz, CDCl3): δ 2.10 (6H, s(br), (CH3)2N), 2.86 (6H, s(br), (CH3)2N), 3.90 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.08 (2H, d, L-H3,5), 7.22 (1H, t, L-H4), 7.77 (4H, d, Ar-H), 7.63 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.5 (s(br), (CH3)2N), 44.4 (s(br), (CH3)2N), 63.2 (s, (CH2)N), 126.5 (s, L-C3,5), 129.1 (s, Ar-C), 129.8 (s, L-C4), 147.2 (s, L-C2,6), 149.3 (s, Ar-C), 154.9 (s, L-C1), (Ar-C1-B) not observed. Synthesis of 12b. Following the general procedure: (LBiO)2 (98 mg, 0.12 mmol) and 4-PyB(OH)2 (55 mg, 0.48 mmol) in dichloromethane (30 mL) gave 12b, after additional recrystallization, as cream crystalline solid. Yield: 99 mg, 67%. M.p. 105 °C-dec. Anal. calcd for C22H27B2BiN4O3 (MW 626.09): C, 42.2; H, 4.4; Found: C, 42.4; H, 4.5%. 1H NMR (500 MHz, CDCl3): δ 2.18 (6H, s, (CH3)2N), 2.93 (6H, s, (CH3)2N), 4.04 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.32 (1H, t, L-H4), 7.45 (2H, d, L-H3,5), 7.79 (4H, d, Ar-H), 7.62 (4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 42.4 (s, (CH3)2N), 46.1 (s (CH3)2N), 65.5 (s, (CH2)N), 128.6 (s, L-C3,5), 129.2 (s, L-C4), 129.3 (s, Ar-C), 149.1 (s, Ar-C), 152.2 (s, L-C2,6), (L-C1) and (Ar-C1-B) not observed. Synthesis of 12c. Following the general procedure: L(Ph)Sn(CO3) (41 mg, 0.09 mmol) and 4-PyB(OH)2 (22 mg, 0.18 mmol) in dichloromethane (30 mL) gave 12a as cream crystalline solid. Yield: 49 mg, 89%. M.p. 110–112 °C. Anal. calcd for C28H32B2N4O3Sn (MW 612.09): C, 54.8; H, 5.2; Found: C, 54.9; H, 5.3%. 1H NMR (500 MHz, CDCl3): δ 2.23 (12H, s(br), (CH3)2N), 3.83 (4H, AX pattern, 2JH–H = 13.2 Hz, (CH2)N), 7.13 (2H, d, L-H3,5), 7.30 (1H, t, L-H4), 7.45 (3H, d, Ar-H), 7.71 (2H, d, Ar-H), 7.84 (4H, d, Ar-H), 8.63(4H, d, Ar-H). 13C{1H} NMR (100.61 MHz, CDCl3): δ 44.9 (s(br), (CH3)2N), 63.0 (s, (CH2)N), 126.9 (s, Ph-C3,5), 128.8 (s, L-C3,5), 129.1 (s, Ar-C), 129.9 (s, L-C4), 130.4 (s, Ph-C4), 134.4 (s, Ph-C2,6), 138.7 (s, Ph-C1), 141.1 (s, L-C1), 144.9 (s, L-C2,6), 146.2 (Ar-C1-B), 149.0 (s, Ar-C). 119Sn NMR (MHz, CDCl3): δ −366.4. X-ray crystallography The suitable single-crystal of studied compounds were mounted on glass fibre with an oil and measured on fourcircle diffractometer KappaCCD with CCD area detector by monochromatized MoKα radiation (λ = 0.71073 Å) at 150(1) K. The numerical26 absorption corrections from crystal shape were applied for all crystals. The structures were solved by the direct method (SIR92)27 and refined by a full matrix least

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squares procedure based on F2 (SHELXL97).28 Hydrogen atoms were fixed into idealized positions (riding model) and assigned temperature factors Hiso(H) = 1.2Ueq ( pivot atom) or of 1.5Ueq for the methyl moiety with C–H = 0.96, 0.97, and 0.93 Å for methyl, methylene, and hydrogen atoms in aromatic ring, respectively. The only exception is the NH2 group of compound 10a, where the hydrogen atoms were placed according to the maxima on the Fourier difference electron density map. Two NH groups remain without a hydrogen bond acceptor in this molecule. The independent CF3 groups in both 2a and 2b are seriously disordered in sense of positions of fluorine atoms and localization of these maxima to the four different positions had not positive influence to the evaluation parameters. Thus, the electron densities attributed to these groups remain untreated. There are disordered solvent (benzene) molecules in the structure of 12c. Attempts were made to model this disorder or split it into two positions, but were unsuccessful. PLATON/SQUEZZE29 software was used to correct the data for the presence of disordered solvent. A potential solvent volume of 1182 Å3 was found. 173 electrons per unit cell worth of scattering were located in the void. The calculated stoichiometry of solvent was calculated to be four molecules of benzene per unit cell, which results in 168 electrons per unit cell. The same method was also applied in the structure of 9c, but it resulted only in few electrons per unit cell. In this structure, also the EADP from SHELXL9725 software instructions were used to correct two carbon atoms from the toluene solvate molecules, which revealed no positive results. Crystallographic data for structural analysis are given in Table S1† and has been deposited with the Cambridge Crystallographic Data Centre, CCDC no. 963753–963761.

Acknowledgements The authors thank the Grant agency of the Czech Republic project no. P207/13-00289S.

References 1 For examples and reviews see: (a) J. Beckmann and K. Jurkschat, Coord. Chem. Rev., 2001, 215, 267 and references cited therein; (b) J. Beckmann, K. Jurkschat and D. Schollmeyer, in Organosilicon Chemistry III — From Molecules to Materials, ed. N. Auner and J. Weis, 1997, p. 403; (c) J. Beckmann, D. Dakternieks, A. E. K. Lim, K. F. Lim and K. Jurkschat, THEOCHEM, 2006, 761, 177; (d) Y. Li, J. Wang, Y. Wu, H. Zhu, P. P. Samuel and H. W. Roesky, Dalton Trans., 2013, 42, 13715; (e) Z. Padělková, P. Švec, H. Kampová, J. Sýkora, M. Semler, P. Štěpnička, S. Bakardjieva, R. Willem and A. Růžička, Organometallics, 2013, 32, 2398; (f ) C. M. McMahon, S. J. Obrey, A. Keys, S. G. Bott and A. R. Barron, J. Chem. Soc., Dalton Trans., 2000, 2151; (g) S. Geissmann, S. Blaurock, V. Lorenz and F. T. Edelmann, Inorg. Chem., 2007, 46, 10956;

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