MONOPENTAMETHYLCYCLOPENTADIENYL ISOCYANIDE, AMINE AND IMIDO TANTALUM(V) COMPLEXES - X-RAY CRYSTAL-STRUCTURE OF [TACP(ASTERISK)CL(4)(CN-2,6-ME(2)C(6)H(3))]

[TaCp*Cl-4] (Cp*=eta(5)-C(5)Me(5)) reacts with isocyanides and amines to give the pseudo-octahedral adducts [TaCp*Cl(4)L] (L = 2,6-Me(2)C(6)H(3)NC, 1; 2,4,6-Me(3)C(6)H(2)NC, 2; (t)BuNC, 3; or C6H5NH2, 4). Reduction of 1, or alternatively of [TaCp*Cl-4] in the presence of stoichiometric amounts of isocyanide, with two equivalents of Na/Hg gives the diamagnetic pseudo-octahedral tantalum(III) complex, [TaCp*Cl-2(CN-2,6-Me(2)C(6)H)(3)](3) 5. Reaction of 4 with two equivalents of LiNEt(2) affords the pseudo-octahedral imido complex [TaCp*Cl-2(N-C6H5)]. 6. All the complexes were characterized by usual IR and NMR spectroscopic methods and the molecular structure of 1 was confirmed by X-ray diffraction methods.