ZIRCONOCENE DERIVATIVES WITH DIPHOSPHINOMETHANIDE LIGANDS - SYNTHESES OF THE CHELATE COMPLEXES CP2(CL)ZR[(R2P)2CX] AND X-RAY STRUCTURE DETERMINATIONS FOR R = ME, PH AND X = SIME3

The novel four-membered chelate complexes CP2(Cl)Zr[(R2P)2C(X)] (R = Me, X = SiMe3 (4); R = Ph, X = SiMe3 (5), R = Ph, X = H (6)) have been prepared from Cp2ZrCl2 and the appropriate lithium diphosphinomethanides in Et2O. The compounds have been characterized by their NMR spectra and by X-ray structure determinations of 4 and 5. 4: monoclinic, P2(1)/c, a = 16.284 (3) angstrom, b = 14.463 (2) angstrom, c = 19.252 (2) angstrom, beta = 97.42 (1)-degrees, V = 4496.2 angstrom3, Z = 8, T = 22-degrees-C, R(w) = 0.073. w = 1/sigma2(F(o)). 5.2(toluene): monoclinic, P2(1)/n,a = 19.184 (3) angstrom, b = 11.668 (2) angstrom, c = 22.695 (3) angstrom, beta = 114.63 (1)-degrees, V = 4617.8 angstrom3, Z = 4, T = -50-degrees-C, R(w) = 0.050. In both 4 and 5, the Cp2(Cl)Zr moiety is coordinated by the [(R2P)2C(SiMe3)]-ligands via both P atoms (eta2(P,P)), thus forming a four-membered ring. The Zr-P distances are rather long and inequivalent (4, 2.844 (5)/2.721 (5) and 2.823 (4)/2.719 (5) angstrom for two independent molecules; 5, 2.852 (1)/2.817 (1) angstrom). The inequivalence of the phosphorus nuclei and the weak Zr-P interaction in 4-6 can also be deduced from the P-31 NMR spectra. These also reveal that 6 is not in equilibrium with the eta2(C,P)-coordinated complex, which is at variance with the respective findings for Cp2(Cl)Zr[(PMe2)2CH].