The first examples of eta(5)-bonding of a carbaborylphosphine ligand to transition metals. Synthesis and characterisation of 7-{PPh2AuPPh3}-8-Ph-7,8-nido-C2B9H10, 1-{PPh2AuCl}-2-Ph-3-(p-cymene)-3,1,2-pseudocloso-RuC2B9H9 and1-{PPh2AuCl}-2-Ph-3-(eta-C5Me5)-3,1,2-pseudocloso-RhC2B9H9

The close carbaborylmonophosphine 1-PPh2-2-Ph-1,2-closo-C2B10H10 is deboron ated by reaction with ClAuPPh3 in refluxing ethanol to afford the zwitterio nic compound 7-{PPh2AuPPh3}-8-Ph-7,8-nido-C2B9H10, characterised by NMR spe ctroscopy and X-ray crystallography. Deprotonation of this species using Na H in THF followed by reaction with either [(p-cymene)RuCl2](2) or [(eta-C5M e5)RhCl2](2) yields the compounds 1-{PPh2AuCl}-2-Ph-3-(p-cymene)-3,1,2-RuC2 B9H9 and 1-{PPh2AuCl}-2-Ph-3-(eta-C5Me5)-3,1,2-RhC2B9H9, respectively. Thes e latter products, which on the basis of B-11-NMR spectroscopy and (in the first case) a single crystal diffraction analysis, have pseudocloso structu res, are the first reported examples of compounds in which a carbaborylphos phine ligand is eta(5)-bonded to a transition metal. (C) 1999 Elsevier Scie nce S.A. All rights reserved.