ZIRCONOCENE DERIVATIVES WITH PHOSPHINOMETHANIDE LIGANDS - SYNTHESIS, REACTIONS, AND MOLECULAR-STRUCTURES OF CP2ZR(CL)[C(PME2)(X)(Y)] (X = H, Y = PME2, SIME3 X = Y = SIME3)

From CP2ZrCl2 and the appropriate lithium phosphinomethanides, the novel complexes CP2Zr(Cl)[C-(PMe2)(X)(Y)] (X = H, Y = PMe2 (4); X = H, Y = SiMe3 (5); X = Y = SiMe3 (6)) are obtained as crystalline solids and characterized by spectroscopy and by X-rav structure determinations. 4: monoclinic, P2(1)/n, a = 16.080 (2) angstrom, b = 14.047 (1) angstrom, c = 17.003 (2) angstrom, beta = 116.64 (1)-degrees, V = 3432.9 angstrom3, z = 8, T = -35-degrees-C, R(w) = 0.030, w = 1/sigma2(F(o)). 5: monoclinic, P2(1)/c, a = 15.687 (2) angstrom, b = 15.898 (2) angstrom, c = 16.165 (2) angstrom, beta = 111.16 (1)-degrees, V = 3759.6 angstrom3, Z = 8, T = -35-degrees-C, R(w) = 0.061. 6.0.5(toluene): monoclinic, P2(1)/c, a = 18.585 (2) angstrom, b = 8.809 (1) angstrom, c = 16.102 (2) angstrom, beta = 103.93 (1)-degrees, V = 2558.6 angstrom3, Z = 4, T = -40-degrees-C, R(w) = 0.053. In all three complexes 4-6, the zirconium atom as part of a metallaphosphacyclopropane ring is the most prominent structural feature. Whereas the Zr-P (4, 2.621 (1)/2.632 (1) angstrom; 5, 2.634 (1)/2.616 (1) angstrom; 6, 2.606 (1) angstrom) as well as the Zr-Cl (4, 2.569 (1)/2.576 (1) angstrom; 5, 2.558 (1)/2.572 (1) angstrom; 6, 2.554 (1) angstrom) and the Zr-D distances (where D denotes the centroid of the cyclopentadienyl rings; 4, 2.42/2.22 and 2.22/2.24 angstrom; 5, 2.24/2.24 and 2.23/2.24 angstrom; 6, 2.23/2.26 angstrom) are nearly equal, the Zr-C(l) distances differ considerably in going from 4 (2.413 (2)/2.408 (2) angstrom) to 5 (2.401 (5)/2.423 (5) angstrom) and to 6 (2.607 (1) angstrom), due to steric congestion. Consequently, 6 exists in solution as an eta1(P)-coordinated 16e complex, as may be deduced from NMR data. Complex 4 exists in solution as an equilibrium mixture of isomers 4 and 4a, the latter exhibiting a chelating P,P-coordination of the diphosphinomethanide ligand, thus forming the four-membered heterocycle Zr-P-C-P. At elevated temperatures, all phosphorus nuclei equilibrate, obviously via a common intermediate of 4 and 4a. Complexes 4 and 5 do not react with CO at ambient temperature and pressure, whereas 6 decomposes above 0-degrees-C in solution.