Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 79. Synthesis and reactions of the alkylidynemetal complexes [M(≡CR)(CO)2(η-C5H5)] (R = C6H3Me2-2,6, M = Cr, Mo, or W; R = C6H4Me-2, C6H4OMe-2.

Stephen J. Dossett, Anthony F. Hill, John C. Jeffery, Frank Marken, Paul Sherwood, F. Gordon A. Stone

Research output: Contribution to journalArticle

Abstract

The alkylidynemetal complexes [M(≡CR)(CO)2(η-C5H5)] (M = Cr, Mo, or W, R = C6H3Me2-2,6; M = Mo, R = C6H4Me-2, C6H4OMe-2, or C6H4NMe2-4) have been prepared, and several of their reactions have been studied. New compounds characterised include [M{C(C6H3Me2-2,6)C(O)}(CO)(PR′ 3)(η-C5H5)] (M = Mo, R′ = Ph; M = W, R′ = Me), [M(≡CC6H3Me2-2,6)(CO)(PR′ 3)(η-C5H5)] (M = Mo, R′ = Ph; M = W, R′ = Ph or Me), and [MCo23-CC6H3Me 2-2,6)(CO)8(η-C5H5)] (M = Mo or W). However, the main study involved reactions of the alkylidynemetal compounds with [Fe2(CO)9]. The latter with [M(≡CC6H3Me2-2,6)(CO) 2(η-C5H5)] yields the electronically unsaturated (32 valence electron) dimetal compounds [MFe(μ-CC6H3Me2-2,6)(CO) 5(η-C5H5)]. In CO-saturated solutions, these products afford labile saturated (34 valence electron) complexes [MFe(μ-CC6H3Me2-2,6)(CO) 6(η-C5H5)], which readily revert to the unsaturated species in the absence of CO. In contrast, reactions between [Fe2(CO)9] and [Mo(≡CR)(CO)2(η-C5H5)] (R = C6H4Me-2 or C6H4OMe-2) afford the saturated dimetal compounds [MoFe(μ-CR)(CO)6(η-C5H5)]. However, the species with R = C6H4Me-2 in CH2Cl2 solution under a stream of nitrogen yields the labile unsaturated compound [MoFe(μ-CC6H4Me-2)(CO)5(η-C 5H5)]. Moreover, an additional feature of the reaction between [Fe2(CO)9] and [Mo(≡CC6H4Me-2)(CO)2(η-C 5H5)] is the formation of the trimetal compound [MoFe23-CC6H 4Me-2)(μ-CO)(CO)8(η-C5H5)], a product produced in high yield if an excess of the iron carbonyl is used. The reaction between [Mo(≡CC6H4NMe2-4)(CO) 2(η-C5H5)] and [Fe2(CO)9] gives a mixture of [MoFe(μ-CC6H4NMe2-4)(CO) 6(η-C5H5)], [MoFe23-CC6H4NMe 2-4)(μ-CO)(CO)8(η-C5H5)], and [Mo2{μ-C2(C6H4NMe 2-4)2}(CO)6(η-C5H 5)2]. The n.m.r. spectra of the various complexes are discussed. The molecular structure of the unsaturated compound [MoFe(μ-CC6H3Me2-2,6)(CO) 5(η-C5H5)] has been established by an X-ray diffraction study [Mo-Fe 2.577(1), μ-C-Mo 1.976(2), and μ-C-Fe 1.861(2) Å]. Extended-Hückel molecular-orbital calculations have been carried out on model compounds, in an attempt to understand the nature of the bonding between the core M(μ-C)Fe atoms in the 32- and 34-valence-electron dimetal compounds. The results favour a dimetallacyclopropene description for the saturated complexes, and in affect a four-electron donation from the C≡M unit to the Fe(CO)3 groups in the unsaturated compounds. During the course of the work the complexes [WFe(μ-CC6H3Me2-2,6)(CO) 4(PMe3)(η-C5H5)], [WFe(μ-CC6H3Me2-2,6)(μ-CO)(CO) 2(PMe3)2(η-C5H5)], and [WFe(μ-CC6H3Me 2-2,6)(μ-dppm)(μ-CO)(CO)2(η-C5H 5)] (dppm = Ph2PCH2PPh2) were also prepared.

Original languageEnglish
Pages (from-to)2453-2465
Number of pages13
JournalJournal of the Chemical Society, Dalton Transactions
Issue number9
DOIs
Publication statusPublished - 1 Dec 1988

ASJC Scopus subject areas

  • Chemistry(all)

Cite this