THE PREPARATION AND CRYSTAL-STRUCTURES OF THE COMPOUNDS (PH(2)MESI)(3)CMCL (M=ZN, CD, OR HG)

The compounds (PhMe(2)Si)(3)CMCl (M = Zn, Cd, or Hg) have been prepared by reaction of (PhMe(2)Si)(3)CLi with the chlorides MCl(2); for M = Zn or Cd they were obtained via (isolated) Li-containing intermediates thought to [(PhMe(2)Si)(3)CM(mu-Cl)(2)Li(THF)(2)]. The crystal structures of all three compounds [(PhMe(2)Si)(3)CMCl have been determined. The zinc and cadmium chlorides are present in the crystal as the dimers [(PhMe(2)Si)(3)CM(mu-Cl)(2)MC(SiMe(2)Ph)(3)], with the metals three-coordinate in a planar environment (for M = Zn, the C-M-Cl angles average 136 degrees, and the Cl-M-Cl angles 88 degrees; for M = Cd the corresponding values are 137 degrees and 86 degrees) and the chloride bridges slightly unsymmetrical. The cadmium compound is also dimeric in solution in benzene. The compounds appear to be the first structurally characterized organo-zinc or -cadmium halides in which the metal is three-coordinate. The mercury compound also forms dimers in the solid, but the geometry is almost that expected for two-coordinate mercury (the C-Hg-Cl angles at the two metal centres are 171.0(3) and 171.3(3)degrees), with a very weak intermolecular Hg...Cl interaction (mean distance 3.29 Angstrom). The conformations of the (PhMe(2)Si)(3)C groups in all three compounds are discussed.