SYNTHESIS AND PROPERTIES OF S-ALKYL-SUBSTITUTED SILANEDIYL-BRIDGED AND SILANETRIYL-BRIDGED DIIRON COMPLEXES, CP-2(CO)(2)FE-2(MU-CO)[MU-SI(X)CHR2] AND CP-2(CO)(2)FE-2(MU-CO)[MU-SI(DMAP)CHR2]I--) (X = H, I R = ET, PH DMAP = 4-(DIMETHYLAMINO)PYRIDINE)(()

Photolysis of 2 molar amounts of CpFe(CO)(2)SiMe3 (= FpSiMe(3), 1) wit h s-alkylsilanes R2CHSiH3 (2a: R = Et; 2b: R = Ph) produces the silyle ne (or silanediyl)-bridged diiron complexes Cp-2(CO)(2)Fe-2(mu-CO)[mu- Si(H)CHR2] (3a: R = Et; 3b: R = Ph) which exist mainly in cis-form. Th e treatment of cis-3 with an excess amount of CH2I2 stereoselectively affords the iodosilylene-bridged diiron complexes Cp-2(CO)(2)Fe-2(mu-C O)[mu-Si(I)CHR2] (4a: R = Et; 4b: R = Ph) in cis-form. The reaction of complexes 4 with 4-(dimethylamino)pyridine (= DMAP) gives the base-st abilized silylyne (or silanetriyl)-bridged diiron complexes Cp-2(CO)(2 )Fe-2(mu-CO)[mu-Si(DMAP)CHR2]I-+(-) (5a: R = Et; 5b: R = Ph) in 35 and 43% yields, respectively. The cis-trans isomerization of complexes 3 was studied under thermal and photochemical reaction conditions. The m olar ratios of the cis and trans isomers of complexes 3 in the thermal equilibrium at 50 degrees C were 95:5 (3a) and 78:22 (3b), respective ly, and in the photostationary state at 10 degrees C were 80:20 and 30 :70, respectively. The structures of complexes 3b and 4b have been cha racterized by X-ray diffraction.