Metallophosphoranes: The hidden face of transition metal-phosphine complexes

Reactions in which metallophosphoranes, of general formula L_nMPR₄, have been implicated as intermediates or possible transition states are reviewed. Such species can be accessed via nucleophilic attack on metal-phosphine complexes, with the source of nucleophile being either external or internal in the form of an anionic co-ligand. The reverse process, transfer of a group from a {PR₄} ligand to a metal, has also been observed with the formation of a metal phosphine. Thus metallophosphoranes have been postulated to play a role in isomerization processes and novel M-X/P-R exchange reactions. Metallophosphoranes have also been implicated in unusual 'phosphine-assisted C-F bond activation' reactions. Recent computational studies on these processes are discussed. © 2010 Elsevier B.V. All rights reserved.