Two Metal−Monocarbollide Relatives of the {B20H18} Double-Cluster Boranes†

Reaction of nine-vertex [closo-1-CB8H9]− with sources of “{M(PEt3)2}+” (M = Rh or Pt) leads to double-cluster metallacarboranes of general formulation [M(PEt3)CB8H9]2, whose gross molecular structures are different but nevertheless isomeric. The two {MCB8} clusters are interconnected by reciprocal B−H⇀M interactions and, in the case of Pt, by a Pt−Pt bond.