Co-ordinatively unsaturated alkyne complexes of tungsten: Synthesis and dynamic nuclear magnetic resonance studies of some but-2-yne derivatives

Jack L. Davidson, Guiseppe Vasapollo

Research output: Contribution to journalArticle

Abstract

Reactions of [{W(µ-Br)Br(CO) (MeC=CMe)2}2] (1) with one molar equivalent of Na(S2CNMe2), Na(S2PMe2), or Tl(acac) (acac = acetylacetonate) give mononuclear derivatives [WBr(L-L)(CO)(MeC=CMe)2] (2) (L-L = S2CNMe2, S2PMe2, or acac). The 1H and 13C n.m.r. spectra of the acac complex are temperature independent whereas dynamic 1H n.m.r. studies of the S2CNMe2 and S2PMe2 derivatives have been interpreted in terms of a molecular rearrangement involving dechelation of the bidentate ligand which exchanges the alkyne environments and the ends of the dithiolate ligand. The reaction of (1) with two molar equivalents of Na(S2PMe2) gives the bis-alkyne complex [W(S2PMe2)2(MeC=CMe)2] (3) whereas Na[S2P(OMe)2] and TI(acac) give mono-alkyne derivatives [W(L-L)2(CO)(MeC=CMe)] (4) [L-L = S2P(OMe)2 or acac]. 1H N.m.r. studies of (3) suggest fluxional behaviour involving dechelation of S2PMe2 which exchanges both the S2PMe2 methyls and the alkyne methyls without necessarily requiring alkyne propeller rotation. In contrast, fluxional behaviour in (4) [L-L = S2P(OMe)2] clearly involves alkyne propeller rotation in addition to two other processes, one of which exchanges the methyl groups of one S2P(OMe)2 group. However, the only dynamic process observed with (4) (L-L = acac) appears to involve alkyne propeller rotation.

Original languageEnglish
Pages (from-to)2855-2863
Number of pages9
JournalJournal of the Chemical Society, Dalton Transactions
Issue number11
DOIs
Publication statusPublished - 1988

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