Carbon-Oxygen Bond Cleavage of Esters Promoted by Hydrido and Alkylcobalt(I) Complexes Having Triphenylphosphine Ligands. Isolation of an Insertion Intermediate and Molecular Structure of Phenoxotris(triphenylphosphine)cobalt(I)

Article abstract of DOI:10.1021/ja00263a007

Carbon-oxygen bonds in aryl and alkyl carboxylates (R'COOR) are selectively cleaved by CoH(N2)(PPh3)3, and carboxylic esters R'COOCH2R' are formed by a Tischchenko type dimerization of aldehyde R'CHO, whereas the reaction of CoMe(PPh3)3 with the esters yields ketones R'COMe.The reaction products are accounted for by assuming insertion of the ester C=O double bond into the Co-H or Co-Me bond, followed by abstraction of the β-alkoxo group by cobalt.The intermediate (β-(ethoxy)alkoxo)cobalt(I) complex Co(OCH(CF3)OEt)(PPh3)3 has been isolated in the reaction of CoH(N2)(PPh3)3 with ethyl trifluoroacetate as well as by alcoholysis of CoH(N2)(PPh3)3 with CF3CH(OEt)OH.Treatment of CoH(N2)(PPh3)3 with phenyl acetate affords a tetrahedral phenoxocobalt(I) complex, Co(OPh)(PPh3)3.Crystals of the complex are monoclinic, space group P2₁/c, with a = 13.142(2) Angstroem, b = 19.661(3) Angstroem, c = 18.714(3) Angstroem, and β = 91.49(3) degree.Block-diagonal least-squares refinement leads to R = 0.075 and R_w = 0.081 for 2966 reflections.The molecular structure of the complexe consists of a tetrahedron with an O-bonded phenoxo group and three PPh3 ligands; the average Co-P distance is 2.320(4) Angstroem and Co-O 1.900(9) Angstroem, and the average P-Co-P angle is 109.9(1) degree, P-Co-O 109.1(4) degree, and Co-O-C 138.2(9) degree, respectively.