MANGANESE-CATALYZED AND RHODIUM-CATALYZED PHENYLSILANE HYDROSILATION-DEOXYGENATION OF IRON ACYL COMPLEXES CP(L)(CO)FEC(O)R (L = CO, PPH3, P(OME)(3), P(OPH)(3) - R = CH3, PH, CHME2, CME3)

The manganese carbonyl acyl complexes L(CO)(4)MnC(O)R (L = CO, R = CH3 (2a); L = CO, R = Ph (2b); L = PPh3, R = CH3 (2c)) are precatalysts f or the PhSiH3 hydrosilation-deoxygenation of Cp(CO)(2)FeC(O)CH3 (1a) t o Cp(CO)(2)FeCH2CH3 (6a). Thus, 2a (4%) and 1.1 equiv of PhSiH3 reduce 1a initially to a mixture of [Cp(CO)(2)FeCH(CH3)O](3-x)HxSiPh (x = 2 (3b), 1 (4b), and 0 (5b)) (7-8 h), which transforms to a mixture of 5b (62%) and 6a (35%) (12 h). Similarly, 2b and PhSiH3 transform la to a mixture containing 4% 3b, 22% 4b, 72% 5b, and 2% 6a (30 min), then up to 15-20% 6a (12 h). Use of 2c as the precatalyst selectively yields 71% 4b and 10% 6a (30 min), then up to 19% 6a (5 h). Both 4b and 5b we re isolated by size-exclusion chromatography and characterized as mixt ures of four stereoisomers, 4b as a pair of enantiomers having a proch iral center and two meso diastereoisomers with pseudoasymmetric center s and 5b as a diastereomeric pair of enantiomers. The PhSiH3 (1.6 equi v)/RhCl(PPh3)(3) (3%) system conveniently transforms Cp(L)(CO)FeC(O)R to their alkyl derivatives Cp(L)(CO)FeCH2R. Seven iron acyl complexes were studied (Cp(CO)(2)FeC(O)R, R = Me, Ph, Pr-i, Bu-t; Cp(L)(CO)FeC(O )CH3, L = PPh3, P(OMe)(3), and P(OPh)(3)), which gave 49-87% isolated yields of Cp(L)(CO)FeCH2R. Their modest yields correspond to the prese nce of byproducts, Cp(CO)(2)FeCH=CH2 (32%) and 4b (14%) with 1a and 10 -15% of the vinyl complexes with L=PPh3 and P(OPh)(3).