MIXED IRON-SILICON-TIN COMPLEXES STABILIZED BY A PHOSPHINOENOLATE BRIDGING LIGAND - CRYSTAL-STRUCTURE OF )(3)((MEO)(3)SI)-FE(MU-PH(2)PCH=C(O)PH)SNBU(N)(2)]

Interesting differences have been observed in the reactivity of mer-[F eH(CO)(3){Si(OMe)(3)}{Ph(2)PCH(2)C(O)Ph}] and er-[FeH(CO)(3){Si(OMe)(3 )}{Ph(2)PCH(2)C(O)NPh(2)}] toward tin derivatives of the type [SnX(2)R (2)]. Whereas the former which contains a diphenylphosphino ketone lig and reacted with [SnCl(2)Bu(2)(n)], [SnBr(2)Bu(2)(n)], [Sn(O(2)CMe)(2) Bu(2)(n)] or [SnCl(2)Ph(2)] to yield only one type of complex [(OC)(3) {(MeO)(3)Si}-Fe{mu-Ph(2)PCH=C(O)Ph}SnR(2)] (R = Bu(n) or Ph), respecti vely, the latter with the (N) over bar,N-diphenyl-2-diphenylphosphinoa cetamide ligand afforded different products depending upon the nature of X in [SnX(2)Bu(2)(n)]. With [SnCl(2)Bu(2)(n)] or [SnBr(2)Bu(2)(n)] the product obtained was (MeO)(3)Si}-Fe{mu-Ph(2)PCH=C(O)NPh(2)}SnBu(2) (n)], but with [Sn(O(2)CMe)(2)Bu(2)(n)] no reaction was observed. The halides appear to be better leaving groups than acetate and this, asso ciated 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.