Neutral organoantimony(III) and organobismuth(III) ligands as acceptors in transition metal complexes – Role of substituents and co-ligands

This article reviews work up until mid-2014 on the synthesis and properties of transition metal complexes containing the heavier Group 15 Sb(III) and Bi(III) ligands, of general formula ER3 (E = Sb or Bi; R = alkyl, aryl etc, and may include a pendant donor group such as amine or ether) and ER(3-n)Xn (E = Sb or Bi; R is an organic substituent such as alkyl, aryl, etc.; X is an electronegative substituent such as halide; n = 0-3) in which these ligands function as a donor to a transition metal fragment, while simultaneously participating as an acceptor to another electronegative group such as an anionic or metal-coordinated halide, or an amine, ether, etc., leading to Sb/Bi centres bearing more than eight valence electrons ('hypervalent'). The Lewis acid properties of the halostibines and halobismuthines, ER(3-n)Xn, are also reviewed.