A novel stibacarbaborane cluster with adjacent antimony atoms exhibiting unique pnictogen bond formation that dominates its crystal packing

Abstract

We have prepared nido-7,8,9,11-Sb 2 C 2 B 7 H 9 , the first cluster with simultaneous Sb-B, Sb-C and Sb-Sb atom pairs with interatomic separations with magnitudes that approach the respective sums of covalent radii. However, the length of the Sb-Sb separation in this cluster is slightly less than the sum of the covalent radii. Quantum chemical analysis has revealed that the crystal packing of nido-7,8,9,11-Sb 2 C 2 B 7 H 9 is predominantly dictated by pnictogen (Pn) bonding, an unconventional σ-hole interaction. Indeed, the interaction energy of a very strong Sb 2 ⋯H-B Pn-bond in the nido-7,8,9,11-Sb 2 C 2 B 7 H 9 dimer exceeds −6.0 kcal mol −1 . This is a very large value and is comparable to the strengths of known Pn-bonds in Cl 3 Pn⋯π complexes (Pn = As, Sb).

Dihalogen and Pnictogen Bonding in Crystalline Icosahedral Phosphaboranes

“…Indeed, various chalcogen and X-bonds have been reported for closo-thiaboranes and halogenated carboranes [9][10][11]. In addition, pnictogen (Pn) bonds are known for various nido-Pn 2 C 2 B 7 H n X 9−n (Pn = P, As, Sb) molecules [12,13]. All these σ-hole interactions have been reported for single crystalline materials.…”

Various types of non-covalent interactions contributing towards crystal packing of halogenated diphospha-dicarbaborane with an open pentagonal belt

“…(2) and nido-7,8,9,11-Sb 2 C 2 B 7 H 9 (3) compounds are already known. [4][5][6] The crystal packing of 3 is governed by Pn-bonds. 6 In contrast to 3, it has not been possible to record the singlecrystal X-ray data of the parent nido-7,8,9,11-P 2 C 2 B 7 H 9 and nido-7,8,9,11-As 2 C 2 B 7 H 9 in sufficient quality.…”

“…[4][5][6] The crystal packing of 3 is governed by Pn-bonds. 6 In contrast to 3, it has not been possible to record the singlecrystal X-ray data of the parent nido-7,8,9,11-P 2 C 2 B 7 H 9 and nido-7,8,9,11-As 2 C 2 B 7 H 9 in sufficient quality. Interestingly, it is feasible to determine the structure of single-crystal halogenated compounds 1 and 2, revealing a supramolecular architecture mainly resulting from extensive Pn-bonding.…”

“…Compound 3 has a binding motif that is exclusively formed by a single Pn-bond and has the DE value of À6.5 kcal mol À1 . 6 The AÁ Á ÁC motif, formed by two symmetrical C-HÁ Á ÁI-B H-bonds, has DE of À6.5 kcal mol À1 . The H-bond is again rather long (3.2 Å).…”

“…Interestingly, it is feasible to determine the structure of single-crystal halogenated compounds 1 and 2, revealing a supramolecular architecture mainly resulting from extensive Pn-bonding. [4][5][6] In order to proceed in the examination of the non-covalent interactions of nido-heteroboranes, we attempted to iodinate 1 (Fig. 1) by the reaction with elemental iodine in the presence of aluminum trichloride (details in ESI †).…”