Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. Part 4. Reactivity studies of the bisallyl complex CpMo(supine-η-C3H5)2 and the allyl-butadiene complex [CpMo(supine-η-C3H5)(supine-η-C4H6)] [PF6] .
Résumé
Compound CpMo(η3-C3H5)2, 3, has been synthesized from CpMoCl4 and four equivalents of allylmagnesium bromide. While the compound is stable 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 ButNC at room temperature affords CpMo(η3-C3H5)(ButNC)2, 4. A similar reduction with presumed allyl radical loss occurs for [CpMo(η3-C3H5)(η4-C4H6)]+, [1c]+, to afford [CpMo(η4-C4H6)(ButNC)2]+, 5. Treatment of [1c]+ with methyllithium affords two products, the major one (1c) corresponding to the one-electron reduction pathway and the minor one (CpMo(η3-C3H5)(η3-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 room temperature Cp2Fe+PF6− oxidation of 3 in MeCN induces the immediate release of 1,5-hexadiene. The oxidation of 3 in ButNC gives complexes [CpMo(CNBut)3 (η2−CH2CHCH2CH2CH=CH2)]+PF6− (7, major) and [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(η3:η3−C3H4CH2CH2C3H4)(CD3CN)]+PF6−, 9, and [CpMo(η4−C4H6)(CD3CN)2]+PF6−, 10. Thermal decomposition of this mixture affords butadiene and 1,5-cyclooctadiene.
Domaines
Chimie de coordination
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