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

• Transition metal stibine and bismuthine complexes with simultaneous donor and acceptor properties are reviewed.
• Lewis acid and Lewis base properties of halostibines and halobismuthines are reviewed.
• Effects of substituent types on structural properties are reviewed.

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.

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