A Direct Route to Halogenated Arsaborane Clusters: Crystal Structure of 3,4,5,6‐Tetrachloro‐1,2‐diarsa‐ closo ‐hexaborane(4)

Copyrolysis of B 2 Cl 4 and AsCl 3 at 330°C leads to the formation of closo ‐1,2‐As 2 B 4 Cl 4 ( 1 ) and further products the mass spectral evidence of which suggests that they are perchlorinated arsaboranes As 2 B 5 Cl 5 , As 4 B 8 Cl 6 , and As 2 B 10 Cl 10 . The pyrolysis temperature and the molar ratio of the reactants exert an essential influence on the type and distribution of the products. At temperatures above 400°C and higher B 2 Cl 4 /AsCl 3 ratios the formation of As 2 B 10 Cl 10 is preferred to that of smaller arsaboranes. A single‐crystal X‐ray study of 1 confirmed that, consistent with its 14‐skeletal electron count, the arsaborane adopts a slightly distorted octahedral structure with the arsenic atoms in adjacent cis positions.