2 ISOMERS OF WCL3(PME2PH)3 AND THEIR POTENTIAL FOR EQUILIBRATION WITHW2CL6(PME2PH)N

A new (comproportionation) synthesis of WCl3(PMe2Ph)3, as well as the coexistence of two structural isomers, is reported. These are characte rized by H-1 NMR spectroscopy and single-crystal X-ray diffraction. Eq uilibration of these two species is effected at 80-degrees-C, with mer converting completely to fac. It is not possible to convert the WCl3L 3 (L = PMe2Ph) species to either of the known dimers W2Cl6Ln (n = 3, 4 ). The mer --> fac isomerization is shown to be catalyzed by WCl4L2 (b ut not by WCl2L4). The mechanism of the comproportionation synthesis O f WCl3L3 strongly favors the mer isomer, and a mechanism is proposed t o account for this. Photolysis of a mixture of [WCl3(PMe2Ph)2]2 in the presence of excess PMe2Ph completely converts the dimer to mer-WCl3(P Me2Ph)3. Mechanistic features which cause the stereoselectivity of thi s reaction are discussed. Cell parameters for fac-WCl3L3 (-165-degrees -C): a = 9.476(2) angstrom, b = 18.091(5) angstrom, c = 9.185(2) angst rom, alpha = 98.62(1)-degrees, beta = 101.53(1)-degrees, gamma = 93.49 (1)-degrees with Z = 2 in space group P1BAR. Cell parameters for mer W Cl3L3 at -155-degrees-C, a = 16.031(3) angstrom, b = 10.297(1) angstro m, c = 17.913(3), beta = 113.86(1)-degrees, Z = 4, and space group P2( 1)/c.