Synthesis and Characterisation of Sigma‐ and Pi‐Bonded Metallaphosphacarboranes

Abstract

Two new metallaphosphacarboranes have been synthesised from [7, 8‐nido‐CPB9H11]– by deprotonation followed by treatment with a metal fragment. Starting with [HNMe3][7, 8‐nido‐CPB9H11] deprotonation and reaction with a source of {(indenyl)Co}2+ affords the η‐bonded cobaltaphosphacarborane 3‐(η‐C9H7)‐3,1,2‐closo‐CoCPB9H10 (1) the first “half‐sandwich“ 3,1,2‐metallaphosphacarborane. The indenyl ligand conformation in 1 (cisoid between the indenyl bridgehead carbon atoms and cage heteroatoms, with the cage carbon atom lying below the indenyl C–C bond) reveals that the structural trans effect in a phosphacarborane ligand is weakest for carbon and therefore varies in the order B > P > C. Starting with [HNC5H11][7, 8‐nido‐CPB9H11] deprotonation and reaction with half an equivalent of [Ru(p‐cymene)Cl2]2 affords the σ‐bonded ruthenaphosphacarborane 8‐{Ru(p‐cymene)Cl(C5H11N)}‐7, 8‐nido‐CPB9H11 (2), the first example of a molecule with a phosphacarborane σ‐bonded to a metal to be crystallographically characterised.