ZIRCONIUM COMPLEXES WITH PHOSPHINOMETHANIDE LIGANDS - SYNTHESES, REACTIVITY, AND X-RAY STRUCTURE DETERMINATIONS

The reactions of ZrCl4 with lithium phosphinomethanides were investiga ted. With LiCH2-PMe2, 1, and Li[CH(PMe2)2], 2, the products could not be characterized satisfactorily. With {(TMEDA)Li[CH(PMe2)(SiMe3)]}2, 3 , a mixture of compounds Cl(4-n)Zr[CH(PMe2)(SiMe3)]n (n = 1-4), 4a-d, was obtained and characterized spectroscopically. Various coordination modes of the phosphinomethanide ligands are observed for n = 3 (4c) a nd n = 4 (4d) by means of NMR spectroscopy. With (TMEDA){Li[C(PMe2)(Si Me3)2]}2, 5, only disubstitution is observed, and Cl2Zr[C(PMe2)(SiMe3) 2]2, 6, containing hexacoordinated Zr, was isolated in high yield as r ed crystals (monoclinic, C2/c, with a = 9.273(1) angstrom, b = 15.078( 2) angstrom, c = 22.062(2) angstrom, beta = 95.09(1)degrees, Z = 4, wR = 0.025). Complex 6 in toluene solution inserts CO into a Zr-C bond, and after a subsequent 1,2-silyl shift a phosphino enolate complex is formed, which dimerizes to give {Cl2Zr[C(PMe2)(SiMe3)2][OC(SiMe3)=C(Si Me3)PMe2]}2, 7(yellow crystals: monoclinic, P2(1)/n, with a = 10.149(1 ) angstrom, b = 16.503 (2) angstrom, c = 19.307(3) angstrom, beta = 97 .13(1)degrees, Z = 2, wR = 0.031). In THF solution 6 also inserts CO, and spectroscopic evidence indicates a mixture of two compounds: the p hosphorusylide (Me3Si)(Me3SiO)C=C(PMe2)PMe2=C(SiMe3)2(=L), 8, and LZrC l2, 9. With the lithium diphosphinomethanides (D)Li[C(PR2)2(SiMe3)] (D = -, R = Me, 5a; D = TMEDA, R = Ph, 5b; D = TMEDA, R = Me, 5c), the h exacoordinate complex Cl2Zr[ C(PMe2)2(SiMe3)]2, 10, and the ionic spec ies [(TMEDA)2Li]{Cl3Zr[C(PR2)2(SiMe3)]2}, 11 (R = Ph) and 12 (R = Me), with heptacoordinated zirconium are obtained, and the latter both wer e characterized by X-ray structure determinations: 11, red crystals, o rthorhombic, Pbca with a = 19.016(2) angstrom, b = 32.385(4) angstrom, c = 23.906(3) angstrom, Z = 8, wR = 0.070; 12.2MePh, red crystals, mo noclinic, P2(1)c with a = 16.138(2) angstrom, b = 13.837(1) angstrom, c = 25.779(3) angstrom, beta = 102.19(1)degrees, Z = 4, wR = 0.051.