X-ray crystal structure of the mononuclear tris(trimethyl phosphite)(maleic anhydride)cobalt(0) complex

Article abstract of DOI:10.1021/om00077a010

The crystal structure of a new mononuclear cobalt(0) complex with trimethyl phosphite and maleic anhydride (MA) ligands has been determined from X-ray diffractometer data. The crystals are monoclinic of space group P2₁/c with Z = 4 in a unit cell of dimensions a = 9.517 (4) ?, b = 15.432 (14) ?, c = 16.915 (8) ?, and β = 113.17 (6)°. The structure was solved by direct and Fourier methods and refined by full-matrix least-squares techniques to R = 0.063 for 2726 independent reflections. The metal is linked to three P atoms of the trimethyl phosphite groups and to the CH=CH moiety of MA. The molecular structure of C₁ symmetry contains a pseudotetrahedrally coordinated Co atom with bond distances Co-P(mean) = 2.172 (2) ?, Co-C(olefinic)(mean) = 2.033 (7) ?, and Co-X = 1.898 ? and bond angles P-Co-P(mean) = 99.4 (4)° and P-Co-X 117.4° (X is the midpoint of the olefinic bond). The parameters and bonding of the (trimethyl phosphite)cobalt part of the complex are standard with a mean P-O distance of 1.594 (6) ? and indicates a certain degree of π bonding. The mean O-C bond length is 1.443 (12) ?; Co-P-O angles average to 117.1 (2)° and O-P-O to 100.6 (5)°. The bond lengths in the MA ring (with C_s symmetry) indicate strong π-electron delocalization, in accordance with the large decrease in v(C=O) from 1780 and 1850 cm^-1 in free MA to 1722 and 1787 cm^-1 in the complex.