Steric Effects in Heteroboranes. VI. 1‐Ph‐2‐tBuMe2Si‐1,2‐closo‐C2B10H10

The new icosahedral closo-dicarbaborane 1-phenyl-2-(tert-butyldimethylsilyl)-1,2-dicarba-closo-dodecaborane(12), C 14 H 30 B 10 Si, has been prepared and its structure determined by a crystallographic study. Although some relief from steric crowding is achieved by a bending back of the cage-bound phenyl substituent, the bulk of the tert-butyldimethylsilyl group severely restricts any bending back of the silyl moiety. In consequence, some deformation of the cage has resulted. Most significantly, the C cage −C cage connectivity suffers a considerable extension: the C(1)−C(2) distance is 1.745 (6) A, one of the longest observed in systems of this type