Abstract
The new compounds [Nb(η6-C7H8)(PMe3)2Cl2]1, [Nb(η-C7H7)(η4-C7H8)(PMe3)]2 and [Nb(η-C7H7)(CO)3]4 have been prepared. The 17-electron compound 1 has been crystallographically characterised and contains mutually trans tertiary phosphine and chloro ligands. Compound 2 contains the first crystallographically characterised η4-cycloheptatriene ligand, the structure of which is discussed in relation to its 13C NMR spectrum and the use of inverse-mode (1H-observed)13C–1H shift correlation NMR spectroscopy. Treatment of 1 with magnesium butadiene reagent gives [Nb(η-C7H7)(η4-C4H6)(PMe3)]3 and photolysis of 4 in the presence of cycloheptatriene gives [Nb(η-C7H7)(η-4-C7H8)(CO)]5. Compound 2 is protonated readily to yield [Nb(η-C7H7)(η5-C7H9)(PMe3)][PF6]6, and reacts with iodomethane to yield paramagnetic [Nb(η-C7H7)(PMe3)2I]7 which is isomorphous with the analogous 16-electron compound [Zr(η-C7H7)(PMe3)2I], but has an unusually long Nb–I bond. Compound 4 reacts with Me2PCH2CH2PMe2(dmpe) to give the monomeric [Nb(η-C7H7)(dmpe)(CO)]9. The analogous compound [Nb(η-C7H7)(PMe3)2(CO)]10 is prepared by reaction of 4 with PMe3. The paramagnetic sandwich complexes [Nb(η-C5H5)(η-C7H7)]11 and [Nb(η-C5H4Me)(η-C7H7)]12 react with 1 equivalent of allyl bromide to yield the diamagnetic bent-sandwich species [Nb(η-C5H5)(η-C7H7)Br]13 and [Nb(η-C5H4Me)(η-C7H7)Br]14 respectively.
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