Syntheses and Crystal Structures of Brominated Polyhedral Arsa- and Phosphaboranes

Publication Type

Journal contribution

Authors

Keller, W.; Einholz, W.; Rudolph, D.; Schleid, T.

Year of publication

2017

Published in

Z. Anorg. Allg. Chemie

Pubisher

Wiley-VCH

DOI

10.1002/zaac.201700051

The synthesis of the perbrominated arsaboranes closo-1,2-As₂B₄Br₄ (1) and closo-1,2-As₂B₁₀Br₁₀ (2) occurs by co-pyrolysis of B₂Br₄ and AsBr₃ at 500 °C. Repeated fractionation of the sublimable products in vacuo yields both compounds in pure form. The X-ray structure determination for orthorhombic closo-1,2-As₂B₄Br₄ (1) [space group: Pbcn, a = 2345.48(17) pm, b = 627.31(4) pm, c = 1294.02(9) pm for Z = 8] and the corresponding phosphorus compound, monoclinic closo-1,2-P₂B₄Br₄ (3) [space group: P2₁/n, a = 806.84(6) pm, b = 1247.96(9) pm, c = 974.91(7) pm, β = 90.493(3)° and Z = 4] confirmed that both 1 and 3, consistent with their 14-skeletal electron counts, adopt octahedral structures distorted from regular by two arsenic or phosphorus atoms in the 1,2-positions. The shortest boron–boron bonds within the cluster frameworks are located between the boron atoms antipodal to the heteroatoms.