MOLECULAR-STRUCTURES AND CHARGE-TRANSFER COMPLEXES OF BENZO[C,H]-1,6-DISILABICYCLO[4.4.0]DECA-3,8-DIENES AND BI(BENZO[C]SILACYCLOPENT-3-ENE-1-YL)S

The reaction of the di-Grignard reagent of alpha,alpha'-dichloro-o-xyl ene with Cl2RSiSiRCl2 (R =(i)Pr and Me) produced 1,6-dialkyl-1,6-disil abicyclo[4.4.0]deca-3,8-diene (1) and bi(benzo[c]-1-alkylsilacyclopent -3-ene-1-yl) (2). The structures of 1a (R = (i)Pr) and 2a (R =(i)Pr) w ere determined by X-ray crystallography. Crystal data for 1a: orthorho mbic, Pbca, a = 14.816(1), b = 16.263(1), c = 17.257(1) angstrom, V = 4158.1(3) angstrom3, Z = 8, R = 0.040, R(w) = 0.050 for 2008 reflectio ns. Crystal data for 2a: triclinic, P1BAR, a = 8.179(2), b = 10.389(3) , c = 6.605(2) angstrom, alpha = 100.39(2)degrees, beta = 98.29(2)degr ees, gamma = 106.75(2)degrees, V = 517.0(3) angstrom3, Z = 1, R = 0.04 2, R(w) = 0.051 for 1167 reflections. Compounds 1 and 2 have relativel y low oxidation potentials (1.24-1.59 V vs. SCE, in acetonitrile) and form charge-transfer complexes with tetracyanoethylene (TCNE). In the case of 2a, the charge-transfer complex was isolated as red crystals a nd the structure was determined by X-ray crystallography. Crystal data for the 2a-TCNE complex: triclinic, P1BAR, a = 6.8399(8), b = 8.2836( 6), c = 12.868(1) angstrom, alpha = 84.142(6), beta = 88.737(6)degrees , gamma = 66.801(8), V= 666.5(1) angstrom3, Z = 1, R = 0.038, R(w) = 0 .042 for 1554 reflections.