Mononuclear derivatives of hexacarbonyl metallates, M(CO)6 (M=Cr, Mo, W), with the multidentate ligand tri-(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3

The reactions of THF-stabilized pentacarbonylmetal fragments, [M(CO)(5)], with P(C7H7)(3) (1) at room temperature lead to normal phosphane complexes, M(CO)(5)[P(C7H7)(3)] (M = Cr (3a), Mo (3b), W (3c)). Upon irradiation in ethereal solution, 3a-c are converted to tetracarbonylmetal derivatives, M(CO)(4)[P(C7H7)(2)(eta(2)-C7H7)] (M = Cr (4a), Mo (4b), W (4c)) in which one of the three cycloheptatrienyl substituents of the ligand 1 is symmetrically coordinated as a mono-olefinic side-chain. On the other hand, the reactions of donor-stabilized tricarbonylmetal fragments, [M(CO)(3)], with 1 give complexes of the type M(CO)(3)[P(C7H7)(2)(eta(4)-C7H7)] (M = Cr (5a), Mo (5b), W (5c)) which contain one of the three ring substituents of 1 coordinated in the eta(4)-norcaradiene form. In the case of 5a, subsequent irradiation in ether solution led to compound Cr(CO)(2)[P(C7H7)(eta(2)-C7H7)(eta(4)-C7H7)] (6a) where 1 is acting as an eight-electron ligand. Displacement of the acetonitrile ligands from the tropylium half-sandwich [(eta(7)-C7H7)MO(CH3CN)(3)]BF4 by P(C7H7)(3) (1) gave {(eta(7)-C7H7)Mo[P(C7H7)(2)(eta(4)-C7H7)]}BF4 (7b). The new complexes were characterized by their H-1, C-13 and P-31 NMR spectra, and the molecular structure of 5a has been confirmed by an X-ray crystal structure analysis.