A pentuply-bridging carbonyl group: crystal and molecular structure of a salt of the 1-oxo-2-phenyl-1,2-dicarbadodecaborate(12) anion, [LH] + [O(Ph)C 2 B 10 H 10 ] – (L = 1,8-N,N,N′,N′-tetramethylnaphthalenediamine)

Deprotonation of the C-hydroxy ortho-carborane 1,2-HO(Ph)C2B10H10 by 1,8-N,N,N′,N′-tetramethylnaphthalene-diamine gives a salt whose anion, [O(Ph)C2B10H10]–, effectively consists of a nido-shaped [PhCB10H10]– residue capped by a pentuply-bridging carbonyl group whose C–O distance of 1.245(3)Å and position over the open carborane face, 2.001(3)Å from the cage carbon atom, are readily rationalized by frontier orbital considerations.