Homonuclear dinickel complexes: structural mimics for the dinickel subsite of the A-cluster of acetyl-CoA synthase

[Ni(ema)(μ-S,S′)Ni(dppp)] (1) and [Ni(ema)(μ-S,S′)Ni(dppe)] (2) have been prepared as synthetic structural analogues of the Ni–Ni subsite of the A-cluster of the enzyme acetyl-CoA synthase by reaction of [Ni(ema)]2−, H4ema is N,N′-ethylenebis(2-mercaptoacetamide), with [NiCl2(diphos)], diphos is 1,2-bis(diphenylphosphino)propane (dppp) or 1,2-bis(diphenylphosphino)ethane (dppe). A similar reaction with 1,2-bis(diethylphosphino)ethane did not give the dinuclear product but the trinuclear complex [NEt4]2[Ni{Ni(ema)(μ-S,S′)}2] (3). Complexes 1 and 3 have been crystallographically characterised.