HALF-SANDWICH ISOCYANIDE, PHOSPHINE, METHYL AND PHOSPHANIDO PENTAMETHYLCYCLOPENTADIENYLNIOBIUM(V) COMPLEXES

[NbCpCl4] (Cp* = eta(5)-C(5)Me(5)) reacts with one molar equivalent o f isocyanides and phosphines to give pseudo-octahedral adducts [NbCpC l-4 . L], (L = 2,4,6-Me(3)C(6)H(2)NC, 1; PMe(3), 2; PMe(2)Ph, 3; PMePh (2), 4) and the dinucIear complex [(hTbCpCl-4)(2)(mu-dmpe)], 5. React ions of [NbCpCl-4] with appropriate amounts of MgClMe yield the corre sponding dimethyl [NbCpCl(2)Me(2)], 6, and tetramethyl [NbCp*Me(4)], 7 derivatives. Similarly, when [{NbCpCl-3}(2)(mu-O)] and 3 are treate d with the allylating magnesium reagent, [{NbCpMe(3)}(2)(mu-O)], 8, a nd [NbCpCl(3)Me(PMe(2)Ph)], 9, are obtained in high yields. A new pho sphanido-niobium(V) complex [NbCpCl-3(PPh(2))] 10, is formed in the r eaction of the starting tetrachloro complex with one equivalent of LiP Ph(2). All the complexes were characterized by IR and NMR spectroscopy , and most of them were studied by mass spectrometry.