Reactions of Co-ordinated Ligands.  Part 27.  Formation of h3-Allyl and s-Vinyl Complexes by Nucleophilic Attack on Cationic Molybdenum Monoacetylene Complexes.  Molecular Structures of [Mo(CO)(PEt3)(h3-anti-1-MeC3H4)(h5-C9H7)] and [Mo{P(OMe)3}3{s-(E)-CHCHBut}(h-C5H5)]

Stephen R. Allen, Paul K. Baker, Stephen G. Barnes, Martin Bottrill, Michael Green, A. Guy Orpen, Ian D. Williams, Alan J. Welch

Research output: Contribution to journalArticle

Abstract

Reaction of [MoLL1(η-MeC2R)A][BF4] [R = Me, Et, or Pri; L = L1 = P(OMe)3; LL1 = Ph2PCH=CHPPh2; L = PEt3, L1 = CO; A = η-C5H5 or η5-C9H7] with NaBH4 or K[BHBus3] in tetrahydrofuran affords the anti-substituted η3-allyl complexes [MoLL13-CH2-...CH-...CHR)A]. The structure of the complex [Mo(CO)(PEt3)(η3-anti-1-MeC3H 4)(η5-C9H7)] was established by single-crystal X-ray crystallography. Crystals are monoclinic, space group P21/n with a = 10.038(2), b = 17.291(4), c = 11.346(3) Å, β = 95.000(18)°, and Z = 4. Using 3 887 reflections measured on a four-circle diffractometer at room temperature, the structure has been refined to R 0.0344, R′ 0.0459. The molecule adopts an exo-conformation with the methyl substituent of the allyl ligand in an anti-position cis to the carbonyl ligand. Treatment of the complex [Mo{P(OMe)3}2(η-HC2Bu t)(η-C5H5)][BF4] with NaBH4 or K[BHBus3] in the presence of excess P(OMe)3 gives the σ-vinyl complex [Mo{P(OMe)3}3{σ-(E)-CH=CHBu t}(η-C5H5)], structurally identified by n.m.r, spectroscopy and X-ray crystallography. Crystals are monoclinic, space group P21/c with a = 11.731(3), b = 12.796(3), c = 18.827(4) Å, β = 92.33(2)°, and Z = 4. Using 7 437 intensity data, measured at 195 K on a four-circle diffractometer, the structure has been refined to residuals R = 0.026, R′ = 0.026. The molecule shows typical four-legged 'piano-stool' geometry with the vinyl group adopting E stereochemistry, σ-bonded to the molybdenum atom. In contrast, the reaction of K[BHBus3] with [Mo{P(OMe)3}2(η-HC2Pr i)(η-C5H5)][BF4] in tetrahydrofuran at low temperature affords the allyl complex [Mo{P(OMe)3}23-1,1-Me2C 3H3)(η-C5H5)]. The n.m.r. spectra and mechanism of formation of these compounds are discussed.

Original languageEnglish
Pages (from-to)927-939
Number of pages13
JournalJournal of the Chemical Society, Dalton Transactions
Issue number5
DOIs
Publication statusPublished - 1983

ASJC Scopus subject areas

  • Chemistry(all)

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