Alkylcobalt carbonyls: XI. Ligand-assisted carbonylation—decarbonylation reactions of alkylcobalt carbonyls

Abstract

An [(alkoxycarbonyl)methyl]cobalt tetracarbonyl (1) derivative (alkyl = Et, 1a) was treated with tertiary phosphorus ligands. A monosubstituted acyl derivative EtOC(O)CH2C(O)Co(CO)3L (2), L = PPh3 (2f) was isolated, and other new complexes of type 2 were detected spectroscopically (L = PEt3, 2a; P(iPr)3, 2c; P(tBu)3, 2d; PMePh2, 2e; P(NEt2)3, 2g; P(OMe)3, 2h; P(OEt)3, 2i; P(OSiMe3)3, 2j; P(SiPr)3, 2k). The corresponding alkyl derivatives, EtOC(O)CH2Co(CO)3L(3), were obtained by thermal decarbonylation. Disubstituted acyl-, EtOC(O)CH2C(O)Co(CO)2L2 (4), and alkyl-, EtOC(O)CH2Co-(CO)2L2 (5) derivatives were obtained by direct substitution at ca. 30°C and ca. 70°C, respectively. The geometries of the new complexes were deduced from spectroscopic data. The monosubstituted derivatives 2 and 3 all show a trigonal bipyramidal array with axial organyl an PR3 ligands. All the disubstituted complexes display a trigonal bipyramidal geometry with axial organyl groups, whereas an axial-equatorial distribution of the phosphines was assigned in the case of compounds 4a, b and 5a, b, e, h, i, and an equatorial-equatorial distribution in the case of complexes 4j and 5g, j. For the alkyl complexes 5 a solvation-like interaction between the ester group and the cobalt atom (autosolvation) was indicated by spectroscopic data.