Synthesis, reactions, and dynamic nuclear magnetic resonance studies of η2-vinyl complexes of molybdenum and tungsten, [m{η3-C(CF3)C(CF3)(L-L)}(CF 3C=CCF3)(η5-C5H5)] (L-L = MeCO2-...

Jack L. Davidson

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Abstract

full title:Synthesis, reactions, and dynamic nuclear magnetic resonance studies of ?2-vinyl complexes of molybdenum and tungsten, [m{?3-C(CF3)C(CF3)(L-L)}(CF 3C=CCF3)(?5-C5H5)] (L-L = MeCO2-, Me2PS2-, Et2NCS2-, or Me2NCS2-) Reactions of bis(hexafluorobut-2-yne) complexes [MCl(CF3C=CCF3)2(?5-C 5H5)] (M = Mo or W) with anions L-L = MeCO2-, Me2PS2-, and R2NCS2- (R = Me or Et) give adducts [M(L-L)(CF3C2CF3)2(? 5-C5H5)] which exhibit a bis(alkyne) structure containing a monodentate ligand L-L and/or an isomeric ?2-vinyl structure in which the ligand L-L forms a bridge between the metal and the ?2-vinyl ligand. In the cases M = Mo or W, L-L = R2NCS2 (R = Me or Et) the ?2-vinyl structure is stereochemically rigid whereas with M = Mo, L-L = MeCO2- or Me2PS2-; M = W, L-L = Me2PS2-, 19F n.m.r. studies reveal fluxional behaviour attributed to reversible cleavage of the (L-L)-?2-vinyl linkage which regenerates the bis(alkyne) structure. Thermolysis of ?2-vinyl complexes [Mo{?3-C(CF3)C(CF3)(L-L)}(CF 3C=CCF3)(?5-C5H 5)] gives tetrakis(trifluoromethyl)cyclobutadiene derivatives [Mo(L-L){?4-C4(CF3)4}(? 5-C5H5)] (L-L = S2CNR2) in which the cyclobutadiene ring exhibits high barriers to rotation about the metal-ligand axis. Complexes of this type can also be obtained from the metathetical reactions of [MoI(CO){?4-C4(CF3)4}(? 5-C5H5)] with metal salts of (L-L)- (S2CNMe2 or pyridine-2-thiolate). Thermolysis of [Mo{?3-C(CF3)C(CF3)S2CNR 2}(CF3C=CCF3)(?5-C 5H5)] also gives small quantities of the ?2-vinyl complex [Mo{?3-C(CF3)C(CF3)C(CF 3)=C(CF3)S}(?2-R2NCS)(? 5-C5H5)] resulting from condensation of the two fluorocarbon units and fragmentation of the R2NCS2 moiety. This type of complex is the major product when the ?2-vinyl complex [Mo{?3-C(CF3)C(CF3)S2CNR 2}(CF3C=CCF3)(?5-C 5H5)] is photolysed in solution.

Original languageEnglish
Pages (from-to)2715-2722
Number of pages8
JournalJournal of the Chemical Society, Dalton Transactions
Issue number11
DOIs
Publication statusPublished - 1987

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Dive into the research topics of 'Synthesis, reactions, and dynamic nuclear magnetic resonance studies of η<sup>2</sup>-vinyl complexes of molybdenum and tungsten, [m{η<sup>3</sup>-C(CF<sub>3</sub>)C(CF<sub>3</sub>)(L-L)}(CF <sub>3</sub>C=CCF<sub>3</sub>)(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)] (L-L = MeCO<sub>2</sub><sup>-</sup>...'. Together they form a unique fingerprint.

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