Phosphorus-carbon bond formation in heterobimetallic molybdenum-tungsten alkyne complexes

Gillian A. Acum, Martin J. Mays, Paul R. Raithby, Gregory A. Solan

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The heterobimetallic complexes [MoW(μ-R1CCR2)(CO)4(η-C 5H5)2] (R1 = H, R2 = Ph 1a, Me 1b or H 1c; R1 = R2 = CO2Me 1d or Me 1e) have been isolated from the reaction of a mixture of [Mo2(CO)6(η-C5H5)2] and [W2(CO)6(η-C5H5)2] with the corresponding alkyne R1C≡CR2 in diglyme (2,5,8-trioxanonane). Thermolysis of complexes 1a-1d with PPh2Cl proceeded via P-Cl bond cleavage and coupling of the diphenylphosphide unit with the alkyne in one of four different ways, depending on the nature of R1 and R2, to give the products [MoW(μ-Cl)(μ-Ph2PCR1=CR2)(CO 2)(η-C5H5)2] (R1 = H, R2 = Ph 2a; R1 = R2 = H 2c or CO2Me 2d), [WMoCl2(μ-Ph2PC=CHR2) (μ-PPh2)(η-C5H5)2] (R2 = Ph 3a, Me 3b or H 3c), [MoWCl2(μ-Ph2PC=CHR2)(μ-PPh 2)(η-C5H5)2] (R2 = Ph 4a or Me 4b) and [WMo(μ-Cl){μ-Ph2PC(CO2Me)=CCO 2Me}(CO)2(η-C5H5)2] 5d. The formation of complexes 2 and 3 can be rationalised as resulting from initial substitution of a molybdenum carbonyl ligand by the halogenophosphine and that of 4 and 5 by initial substitution of a tungsten carbonyl. The significantly higher yield of the former two complexes suggests that initial substitution of a molybdenum carbonyl is the preferred pathway. Attempts at the preparation of an organophosphine-substituted derivative of 1a via its reaction with PPh3 gave [WMo(O)(μ-CH=CHPh)(μ-PPh2)(CO)(η-C5H 5)2] 6 as the only product. A single-crystal X-ray structure determination of complex 3a shows a Mo-W distance compatible with a double bond. The phosphorus atom and the α carbon of the four-membered metallacycle are σ bonded to tungsten and the carbon-carbon double bond is π-co-ordinated to molybdenum.

Original languageEnglish
Pages (from-to)3049-3056
Number of pages8
JournalJournal of the Chemical Society, Dalton Transactions
Issue number18
Publication statusPublished - 31 Dec 1995

ASJC Scopus subject areas

  • Chemistry(all)


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