Macropolyhedral boron-containing cluster chemistry. Ligand-induced two-electron variations of intercluster bonding intimacy. Structures of nineteen-vertex [(η5-C5Me5)HIrB18H19(PMe2Ph)] and the related carbene complex [(η5-C5Me5)HIrB18H19{C(NHMe)2}]

Abstract

Addition of PMe₂Ph to fused-cluster syn-[(η⁵-C₅Me₅)IrB₁₈H₂₀] 1 to give [(η⁵-C₅Me₅)HIrB₁₈H₁₉(PMe₂Ph)] 3 entails a diminution in the degree of intimacy of the intercluster fusion, rather than retention of inter-subcluster binding intimacy and a nido → arachno conversion of the character of either of the subclusters. Reaction with MeNC gives [(η⁵-C₅Me₅)HIrB₁₈H₁₉{C(NHMe)₂}] 4 which has a similar structure, but with the ligand now being the carbene {:C(NHMe)₂}, resulting from a reductive assembly reaction involving two MeNC residues and the loss of a carbon atom.