Mixed iron–silicon–tin complexes stabilized by a phosphinoenolate bridging ligand. Crystal structure of [(OC)3{(MeO)3Si}-Fe{µ-Ph2PCHC(O)Ph}SnBun2]

Abstract

Interesting differences have been observed in the reactivity of mer-[FeH(CO)₃{Si(OMe)₃}{Ph₂PCH₂C(O)Ph}] and mer-[FeH(CO)₃{Si(OMe)₃}{Ph₂PCH₂C(O)NPh₂}] toward tin derivatives of the type [SnX₂R₂]. Whereas the former which contains a diphenylphosphino ketone ligand reacted with [SnCl₂Buⁿ₂], [SnBr₂Buⁿ₂], [Sn(O₂CMe)₂Buⁿ₂] or [SnCl₂Ph₂] to yield only one type of complex [(OC)₃{(MeO)₃Si}-[graphic omitted]nR₂](R = Buⁿ or Ph), respectively, the latter with the N,N-diphenyl-2-diphenylphosphinoacetamide ligand afforded different products depending upon the nature of X in [SnX₂Buⁿ₂]. With [SnCl₂Buⁿ₂] or [SnBr₂Buⁿ₂] the product obtained was [(OC)₃{(MeO)₃Si}-[graphic omitted]nBuⁿ₂], but with [Sn(O₂CMe)₂Buⁿ₂] no reaction was observed. The halides appear to be better leaving groups than acetate and this, associated with the different acidity of the PCH₂ protons between the two phosphine ligands, is responsible for the formation or not of the six-membered ring (Fe–Sn–phosphinoenolate) complex the stability of which constitutes the driving force in the reaction.