Synthesis and reactivity of phosphine-substituted hydrido silyl complexes mer-[FeH(SiR3)(CO)3{Ph2P(CH2)nPPh2}](n= 1 or 4), mer-[FeH{Si(OMe)3}(CO)3(PPh2H)] and mer-[FeH{Si(OMe)3}(CO)3{Ph2PCH2C(O)Ph}]. Synthesis of bimetallic complexes and crystal structure of mer-[(Ph3P)Cu(µ-dppm)Fe{Si(OMe)3}(CO)3

Abstract

Phosphine-substituted hydrido silyl complexes [FeH(SiR3)(CO)3L](L = phosphine) have been prepared by carbonyl substitution in cis-[FeH(SiR3)(CO)4]. The reaction of cis-[FeH{Si(OMe)3}(CO)4]1a with Ph2PCH2PPh2(dppm) in a 1 : 1 ratio afforded mer-[FeH{Si(OMe)3}(CO)3(dppm-P)]2a; mer-[FeH{Si(OEt)3}(CO)3(dppm-P)]2b was obtained similarly. The reaction of [FeH(SiPh3)(CO)4] with Ph2P(CH2)4PPh2(dppb) afforded mer-[FeH(SiPh3)(CO)3(dppb-P)]3a and that of 1a with vinylidenebis(diphenylphosphine)(vdpp) afforded under analogous conditions the chelated complex cis-[FeH{Si(OMe)3}(CO)2(vdpp-PP′)]3c. Reaction of 1a with the functional phosphine Ph2PCH2C(O)Ph yielded mer-[FeH{Si(OMe)3}(CO)3{Ph2PCH2C(O)Ph}]4 and with PPh2H, mer-[FeH{Si(OMe)3}(CO)3(PPh2H)]5 was obtained. The anionic complexes K[Fe(SiR3)(CO)3(PPh2X)]6a(R = OMe, X = CH2PPh2), 6b(R = OEt, X = CH2PPh2), 6c[R = Ph, X =(CH2)4PPh2] and 6d[R = OMe, X = CH2C(O)Ph] were generated from the corresponding hydrido complexes by deprotonation with excess of KH in tetrahydrofuran (thf). They were used to prepare metal–metal bonded heterobinuclear complexes mer-[LM(µ-dppm)Fe{Si(OMe)3}(CO)3]7b(M = Cu, L = PPh3), 7c(M = Cu, L = MeCN), 8a(M = Ag, L = AsPh3), 8b(M = Ag, L = PPh3) and 10(M = Au, L = PPh3). Complex 8a dissociates AsPh3 in solution with formation of mer-[[graphic omitted])Si(OMe)2}(CO)3]9, which contains an unusual alkoxysilyl bridge resulting in a AgFeSiO four-membered ring. This very labile complex was also obtained from the reaction of 6a with [Ag(MeCN)2]NO3. For comparative purposes, we also prepared mer-[(Ph3P)AuFe{Si(OMe)3}(CO)3(PPh3)]11. All complexes were characterized by elemental analysis and spectroscopic (IR and 1H and 31P-{1H} NMR) methods. The crystal structure of compound 7b has been determined by X-ray diffraction: monoclinic, space group P21/c, with a= 11.542(5), b= 18.567(7), c= 21.830(7)A, β= 94.67(2)° and Z= 4. The copper atom is trigonally co-ordinated by two phosphorus atoms from the dppm and PPh3 ligands and by the Fe atom [Fe–Cu = 2.540(2)A]. The Fe atom is in an octahedral arrangement determined by three carbon atoms from carbonyl groups, a phosphorus atom of the bridging dppm ligand and by the Si atom of the Si(OMe)3 group.