EVIDENCE OF THE INTERACTION BETWEEN STERIC AND ELECTRONIC INFLUENCE IN RHODOXIMES AND COBALOXIMES - SYNTHESIS OF PYRH(DH)2I AND X-RAY STRUCTURE OF PYRH(DH)2CL, PYCO(DH)2CL AND PYRH(DH)2I

The crystal structure of pyRh(DH)2Cl (I) and pyCo(DH)2Cl (II) are reported together with the synthesis and the crystal structure of pyRh(DH)2I (III). I: RhClO4N5C13H19; a = 7.5090(8), b =8.588(1), c = 14.479(2) angstrom; alpha = 96.45(8), beta = 87.07(8), gamma = 76.12(9)-degrees; triclinic P1BAR; Z = 2; R = 0.022. II: CoClO4N5C13H19; a = 14.738(2), b = 8.606(1), c = 13.369(2) angstrom; beta = 96.30(1)-degrees; monoclinic Cc; Z = 4; R = 0.022. III: IRhO4N5C13H19; a = 8.875(1), b = 14.741(2), c = 14.163(3) angstrom; beta = 97.47(8)-degrees; monoclinic P2(1)/c; Z = 4; R = 0.031. The Rh-py distance of 2.046(1) angstrom in I, compared to that of 2.079(3) angstrom in III, indicates that I is a slightly better trans-influencing ligand than Cl. The difference in the M-py distances when X = Cl and i-pr is 0.18 angstrom for M = Rh and 0.14 angstrom for M=Co. This result suggests that the interaction between steric and electronic factors is reduced in rhodoximes, owing to the larger size of Rh(III).