SYNTHESIS AND REACTIVITY OF METALLACYCLIC MANGANESE ALPHA-(SILYLOXY)ALKYL COMPLEXES (CO)4MNC(R)(OSI(CH3)3)P(C6H5)2 - A NEW THERMODYNAMIC DRIVING FORCE FOR CO INSERTION
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Reaction of (CO)5MnR(2) with (C6H5)2PSi(CH3)3 (3) gives metallacyclic a-(silyloxy)alkyl complexes (CO)4MnC(R)(OSi(CH3)3)P(C6H5)2(4) in 42-75% yields (R = CH3(a), CH2Si(CH3)3 (b), C6H5 (c), 2-naphthyl (d)). These reactions are of interest in that the metallacyclic carbon is derived from an insertion of CO into the Manganese-carbon bond of 2a step for which subsequent silicon-oxygen bond formation provides an additional thermodynamic driving force. Reaction of (CO)6MnCOC6H5 with 3 also gives 4c (63%). Phosphines (C6H5)3P and 3 react with 2a at nearly the same rate, both separately and in competition experiments. Passage of 4b through wet silica gel gives acyl complex cis-(CO)4Mn(COCH2Si(CH3)3)P(C6H5)2H (6b, 84%), presumably via metallacyclic a-hydroxyalkyl complex (CO)4MnC(CH2Si(CH3)3)(OH)P(C6H5)2(7b). Reaction of 2b with (C6H5)2PH also gives 6b (91%). Reaction of (CO)5MnH and 3 in hexanes gives cis-(CO)4Mn(H)P(C6H5)2Si(CH3)3 (8, 72%). Both 8 and 4a are inert to 300360 psi of CO. The thermodynamics of these transformations are analyzed. 1986, American Chemical Society. All rights reserved.
