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 prepare d 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 struct ures of all three compounds [(PhMe(2)Si)(3)CMCl have been determined. The zinc and cadmium chlorides are present in the crystal as the dimer s [(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 aver age 136 degrees, and the Cl-M-Cl angles 88 degrees; for M = Cd the cor responding values are 137 degrees and 86 degrees) and the chloride bri dges slightly unsymmetrical. The cadmium compound is also dimeric in s olution in benzene. The compounds appear to be the first structurally characterized organo-zinc or -cadmium halides in which the metal is th ree-coordinate. The mercury compound also forms dimers in the solid, b ut the geometry is almost that expected for two-coordinate mercury (th e C-Hg-Cl angles at the two metal centres are 171.0(3) and 171.3(3)deg rees), with a very weak intermolecular Hg...Cl interaction (mean dista nce 3.29 Angstrom). The conformations of the (PhMe(2)Si)(3)C groups in all three compounds are discussed.