CYCLOPENTADIENYLMOLYBDENUM(II) AND CYCLOPENTADIENYLMOLYBDENUM(III) COMPLEXES CONTAINING DIENE AND ALLYL LIGANDS - PART 4 - REACTIVITY STUDIES OF THE BISALLYL COMPLEX CPMO(SUPINE-ETA-C3H5)(2) AND THE ALLYLBUTADIENE COMPLEX [CPMO(SUPINE-ETA-C3H5)(SUPINE-ETA-C4H6)][PF6]

Compound CpMo(eta(3)-C3H5)(2), 3, has been synthesized from CpMoCl4 an d four equivalents of allylmagnesium bromide. While the compound is st able in donor solvents at room temperature, warming in refluxing MeCN induces the formation of 1,5-hexadiene by a metal-mediated allyl-allyl coupling process. Treatment of 3 with (BuNC)-N-t at room temperature affords CpMo(eta(3)-C3H5)((BuNC)-N-t)(2), 4. A similar reduction with presumed allyl radical loss occurs for [CpMo(eta(3)-C3H5)(eta(4)-C4H6) ](+), [1c](+), to afford [CpMo(eta(4)-C4H6)((BuNC)-N-t)(2)](+), 5. Tre atment of [1c](+) with methyllithium affords two products, the major o ne (1c) corresponding to the one-electron reduction pathway and the mi nor one (CpMo(eta(3)-C3H5)(eta(3)-C3H4-1-Et), 6, ca. 4%) corresponding to nucleophilic addition. Protonation of the 1c:6 mixture affords a 2 :1 mixture of cis and trans 2-pentene, in addition to propene. The roo m temperature Cp2Fe+PF6- oxidation of 3 in MeCN induces the immediate release of 1,5-hexadiene. The oxidation of 3 in (BuNC)-N-t gives compl exes [CpMo(CNBut)(3) (eta(2)-CH2=CHCH2CH2CH = CH2)]+PF6- (7, major) an d [CpMo(CNBut)(4)](+) PF6- (8, minor). Finally, the oxidation of 3 in the presence of butadiene, followed by treatment with CD3CN, affords a mixture of [CpMo(eta(3):eta(3)-C3H4CH2CH2C3H4)(CD3CN)]+PF6-, 9, and [ CpMo(eta(4)-C4H6)(CD3CN)(2)]+PF6- 10. Thermal decomposition of this mi xture affords butadiene and 1,5-cyclooctadiene. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.