Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 81. Reactions of the compound [Fe2(µ-CH2)(CO)8] with alkylidyne–molybdenum and –tungsten complexes. Reactivity of the product [WFe{µ-σ:η-CHCH(C6H4Me-4)}(CO)6(η-C5H5)], and crystal structures of the species [W2Fe(µ3-CC6H4Me-4){µ-σ:η-C(C6H4Me-4)Ch2}(CO)6(η-C5H5)2] and [WFe{µ-C(Et)C(Et)C(H)Ch(C6H4Me-4)}(µ-CO)(CO)4(η-C5H5)]

Abstract

Treatment of the compound [Fe₂(µ-CH₂)(CO)₈] in thf (tetrahydrofuran) at room temperature with the reagents [M(CR)(CO)₂(η-C₅H₅)](M = Mo or W, R = C₆H₄Me-4) affords the complexes [MFe{µ-σ:η-CHCH(R)}(CO)₆(η-C₅H₅)] and [W₂Fe(µ₃-CR){µ-σ:η-C(R)CH₂}(CO)₆(η-C₅H₅)₂]. In a similar reaction, the ethylidyne–tungsten compound [W(CMe)(CO)₂(η-C₅H₅)] affords a mixture of [WFe{µ-σ:η-CHCH(Me)}(CO)₆(η-C₅H₅)], [WFe₂(µ₃-CEt)(µ-CO)(CO)₈(η-C₅H₅)], and [W₂Fe(µ₃-MeC₂Me)(CO)₆(η-C₅H₅)₂]. The structure of the species [W₂Fe(µ₃-CC₆H₄Me-4){µ-σ:η-C(C₆H₄Me-4)CH₂}(CO)₆(η-C₅H₅)₂] has been established by X-ray crystallography. The core of the molecule consists of a W₂Fe fragment [W(1)–W(2) 2.895(1), W(1)–Fe 2.738(1), W(2)–Fe 2.827(1)Å], capped by a CC₆H₄Me-4 ligand [W–µ₃-C 2.157(7) and 2.118(6)Å, Fe–µ₃-C 1.998(6)Å], and with the shorter W–Fe vector bridged by a C(C₆H₄Me-4)CH₂ group. The latter is σ bonded to the iron and is η²-co-ordinated to the tungsten. Each tungsten is ligated by a C₅H₅ ligand. Three CO groups are attached to the iron, one to the tungsten bonded by the vinyl group, and two to the remaining tungsten atom. Some reactions of the complex [WFe{µ-σ:η-CHCH(R)}(CO)₆(η-C₅H₅)](R = C₆H₄Me-4) with tertiary phosphines, alkynes, and the platinum reagent [Pt(C₂H₄)₂{P(cyclo-C₆H₁₁)₃}] have been studied. The products characterised include [WFe{µ-σ:η-CHCH(R)}(CO)₅(L)(η-C₅H₅)][L = PPh₃, PMe₃, or dppm (Ph₂PCH₂PPh₂)], [WFe{µ-σ:η-CHCH(R)}(µ-L₂)(µ-CO)(CO)₃(η-C₅H₅)][L₂= dppm or dmpm (Me₂PCH₂PMe₂)], [WFe{µ-C(R′)C(R′)C(H)CH(R)}(µ-CO)(CO)₄(η-C₅H₅)](R′= Et or Me), [WFePt(µ₃-CCH₂R)(CO)₆{P(C₆H₁₁)₃}(η-C₅H₅)], and [WPt{µ-σ:η-CHCH(R)}(CO)₃{P(C₆H₁₁)₃}(η-C₅H₅)]. N.m.r. data are reported and are discussed in relation to the structures proposed. An X-ray diffraction study established the structure of the product [WFe{µ-C(Et)C(Et)C(H)CH(C₆H₄Me-4)}(µ-CO)(CO)₄(η-C₅H₅)] obtained from hex-3-yne. The W–Fe bond [2.798(1)Å] is asymmetrically bridged by a CO ligand [W–C–O 157.5(6)°]. The iron atom carries three terminal CO groups, and the tungsten one such group and the C₅H₅ ring. The metal–metal bond is spanned by a C(Et)C(Et)C(H)CH(C₆H₄Me-4) moiety, the two ends of which are σ bonded to the iron atom, while the C(Et)C(Et)C(H) fragment is η³-co-ordinated to the tungsten centre.