Synthetic, spectroscopic and structural studies on phosphine-stabilised [PPh3, Ph2PCH2PPh2, Ph2P(CH2)4PPh2, (Ph2P)C5H4N] main group element–iron–silicon chain complexes

Abstract

The reaction between K[Fe(CO)₃(PPh₃){Si(OMe)₃}] and InX₃(X = Cl or Br) gave complexes of the type Fe–In(µ-X)₂In–Fe. The chloride-bridged complexes easily form adducts with two-electron donors such as pyridine or OPPh₃. The structure of the chlorobenzene solvate of mer-[(Ph₃P)(OC)₃Fe{µ-Si(OMe)₂([graphic omitted]nCl₂(OPPh₃)] was determined by X-ray diffraction. An oxygen–indium interaction was established which results in a four-membered Fe–Si–O–In ring. This interaction was also evidenced by a variable-temperature ¹H NMR study. The reaction of 2 equivalents of K[Fe(CO)₃(PPh₃){Si(OMe)₃}] with InCl₃ gave the trinuclear complex mer-[graphic omitted]Me)]}₂] which reacts with OPPh₃ to yield mer-[InCl(OPPh₃){Fe(CO)₃(PPh₃)[Si(OMe)₃]}₂]. With GaCl₃ and K[(CO)₃{Si(OMe)₃}(dppm-P)](dppm = Ph₂PCH₂PPh₂) the complex mer-[{(MeO)₃Si}(OC)₃Fe(µ-dppm)GaCl₂] was formed, in which the Fe–Ga bond is stabilised by a bridging dppm ligand. The corresponding complex mer-[{(MeO)₃Si}(OC)₃Fe(µ-dppm)InCl₂] was used in the synthesis of trimetallic complexes of the type mer-[{(MeO)₃Si}(OC)₃Fe(µ-dppm)InCl(M′)][M′= Mo(C₅H₄Me)(CO)₃ or W(C₅H₅)(CO)₃]. The structure of the chlorobenzene solvate of the molybdenum complex was determined by X-ray diffraction. Reaction of K[Fe(CO)₃{Si(OMe)₃}(dppm-P)] and [SnCl₂Ph₂] yielded the trimetallic complexes mer-[SnPh₂{Fe(CO)₃[Si(OMe)₃](dppm-P)}₂] and mer,cis-[Fe(CO)₃(dppm)(SnClPh₂)₂]. The structure of the CH₂Cl₂ solvate of the latter was determined by X-ray diffraction. Bridging by the dppm ligand was deduced from the ¹J(P–Sn) couplings detected by ³¹P-{¹H} NMR spectroscopy. This result Contrasts with the long P–Sn distance of 3.140 Å found in the crystal structure. This complex represents the first Fe–Sn complex containing a bridging dppm ligand. With K[Fe(CO)₃{Si(OMe)₃}{(Ph₂P)C₅H₄N}] the new bimetallic complexes mer-[{[(MeO)₃Si](OC)₃Fe[µ-(Ph₂P)C₅H₄N]Zn(µ-Cl)}₂] and mer-[{(MeO)₃Si}(OC)₃Fe{µ-(Ph₂P)C₅H₄N}MCl₂](M = Ga or In) have been prepared. The reactivity of the first towards donor ligands such as isocyanides or 4-methylpyridine was studied. It also reacts in non-polar solvents with an equivalent of K[Fe(CO)₃(PPh₃){Si(OMe)₃}] to give the trimetallic chain complex [Zn{Fe(CO)₃[Si(OMe)₃][µ-(Ph₂P)C₅H₄N]}₂] which transforms into an ionic species mer-[{(MeO)₃Si}(OC)₃Fe{µ-(Ph₂P)C₅H₄N}Zn][Fe(CO)₃{Si(OMe)₃}{(Ph₂P)C₅H₄N}] in donor solvents like tetrahydrofuran. Complexes containing the cyanometalate (C₅H₄Me) Mn(CO)₂(CN) are also described.