Synthesis and structure of borylated organocobaloximes containing neutral nitrile ligands

The syntheses of the organometallic complexes RCo(DBPh2)(2)(MeCN), where R = Me (1), n-Pr (2), trans-beta-styryl (beta-Sty, 3), and MeCo(DBPh2)(2)TCNE (4) are described. The complexes were characterized by X-ray crystallography. Compound 1 is monoclinic, space group P2(1)/n, a = 9.081(2), b = 14.491(3), c = 14.178(3) Angstrom, beta = 95.35(2)degrees, Z = 2, R = 0.053; compound 2 is monoclinic, space group P2(1)/a, a = 18.973(6), b = 9.369(2), c = 21.059(6) Angstrom, beta = 106.65(2)4 Z = 4, R = 0.079; compound 3 is monoclinic, space group P2(1)/n, a = 15.130(2), b = 16.055(3), c = 15.591(3) Angstrom, beta = 91.70(1)degrees, Z = 4, R = 0.071; compound 4 is triclinic, space group P (1) over bar, a = 15.390(6), b = 15.529(7), c = 18.038(7) Angstrom, alpha = 107.44(2)degrees, beta = 103.54(2) gamma = 101.19(2)degrees, Z = 4, R = 0.058. Compound 1 is found to have an up-down conformation of the equatorial ligand, with one phenyl group facing the Me axial ligand and the other facing the axial MeCN ligand, whereas compounds 2-4 in the solid state show the down-down conformation, with the two axial phenyls of the equatorial ligand facing the neutral one. The present results show that the conformation adopted by these complexes is determined primarily by the difference in bulk between the axial ligands. When the bulk of R is similar to that of L, the pi-pi interactions become the conformational driving force. (C) 1998 Elsevier Science S.A. All rights reserved.