Instability of metal 1,3-benzodi(thiophosphinoyl)methandiide complexes: formation of hafnium, tin and zirconium complexes of 1,3-benzodi(thiophosphinoyl)thioketone dianionic ligand [1,3-C₆H₄(PhPS)₂CS]^2-

The reaction of [LCH₂] (1, L = 1,3-C₆H₄(PhPS)₂) and M(NMe₂)₄ (M = Hf, Zr) in toluene at 110°C afforded a mixture of group 4 metal complexes [{LC(S)}₂M] [M = Hf (2), Zr (3)] and [1,3-C₆H₄(PhPS)(PhP)CH₂]. The reactions appear to proceed through the formation of metal bis(carbene) complexes, [LC=M=CL], which then undergo an intermolecular sulphur transfer reaction with the P=S bond of [LCH₂] to form 2 and 3, and the byproduct is [1,3-C₆H₄(PhPS)(PhP)CH₂]. In addition, the reaction of 1, [CH₂(PPh₂S)₂] (4) and M(NMe₂)₄ in refluxing toluene gave a mixture of [{LC(S)}M(NHMe₂){C(PPh₂S)₂}] [M = Hf (5), Zr (6)], [1,3-C₆H₄(PhPS)(PhP)CH₂] and [CH₂(PPh₂S)(PPh₂)]. Moreover, the intermolecular sulfur transfer reaction is evidenced by the reaction of the tin(ii) 1,3-benzodi(thiophosphinoyl)methandiide complex [{μ-1,3-C₆H₄(PhPS)₂C}Sn]₂ (7) with two equivalents of elemental sulfur in CH₂Cl₂ at ambient temperature to give [{1,3-C₆H₄(PhPS)₂CS}₂Sn] (8). Compounds 2, 3, 5, 6, and 8 were characterized by NMR spectroscopy and X-ray crystallography.