SYNTHESIS, STRUCTURE AND FLUXIONAL BEHAVIOR OF -C5H3-1,3-(SIME(2)CH(2)PPR(2)(I))(2)]ZRCL(3-X)R(X) (R=ME, CH(2)PH, X=0, 1, 3)

The addition of the potentially tridentate ligand [P(2)Cp]Li ([P(2)Cp] Li = (eta(5)-C5H3-1,3-(SiMe(2)CH(2)PPr(2)(i))(2))Li) to ZrCl4(THT)(2) (THT = tetrahydrothiophene) generates [P(2)Cp]ZrCl3. The X-ray crystal structure of this compound is described; crystals are orthorhombic, s pace group P2(1)2(1)2(1) having a = 14.282(2), b = 15.877(3), and c = 13.791(3) Angstrom, Z = 4; the structure was solved by the Patterson m ethod and was refined by full-matrix least-squares to R = 0.032 and R( w) = 0.027 for 2907 reflections with I greater than or equal to 3 sigm a(I). The solution behavior of this compound is consistent with the so lid state structure in that the phosphine arms of the ligand remain co ordinated. Alkylation of [P(2)Cp]ZrCl3 generates the corresponding alk yl complexes [P(2)Cp]ZrCl(3-x)R(x) (x = 1 or 3). In solution [P(2)Cp]Z r(CH(2)Ph)(3) exists in a four-coordinate pseudo-tetrahedral geometry with the two phosphine arms dangling. However, at low temperatures the complexes [P(2)Cp]ZrCl2(CH(2)Ph) and [P(2)Cp]ZrMe(3) exist as five-co ordinate trigonal-bipyramidal structures with one phosphine coordinate d and one phosphine uncoordinated. In these five-coordinate complexes, the coordinated phosphine exchanges with the uncoordinated phosphine via a dissociative pathway and/or an associative pathway depending on the number of hydrocarbyl substituents. The fluxional behavior of thes e complexes was studied by variable temperature P-31{H-1}, C-13{H-1} a nd H-1 NMR spectroscopy, and activation parameters were estimated.