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)Å, 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)Å]. 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.