SYNTHESIS AND X-RAY STRUCTURAL CHARACTERIZATION OF RHCL2(PME2PH)2(C3PH3), THE PRODUCT OF AN OXIDATIVE ADDITION-LIGAND ELIMINATION-REACTION

The Vaska complexes Rh(CO)Cl(PR3)2 (R3=Me3, Me2Ph, MePh2) react with triphenylcyclopropenium salts to generate blue-green rhodiacyclic complexes via oxidative cleavage of the C-C bond. All reactions are accompanied by loss of carbon monoxide. The molecular structure of one such oxidative addition-ligand elimination adduct has been determined by a three-dimensional single-crystal X-ray diffraction study. The title compound crystallizes in the monoclinic space group C2/c with four molecules in a unit cell which measures [FORMULA OMMITED] The structure was solved by heavy-atom techniques and refined by full-matrix, mixed iso/anisotropic least-squares analysis to a conventional R value of 0.041 for the 2550 independent observed (I>2σ(I)) reflections. The Rh(III) adduct displays pseudooctahedral symmetry with trans phosphines, cis chloride ligands, and a bidentate propenylium-1, 3-diyl group. Key bond distances include [FORMULA OMMITED] Structural parameters are compared to the electronically equivalent [IrCl(CO)(PMe3)2(C3Ph3)]+ cation; the M(C3Ph3)+ units in the two structures are noted to be essentially identical. Comparison of Rh(III)-C(sp2) bond lengths in similar complexes suggests a weak but real π component to the Rh-C(propenylium) bond. © 1979, American Chemical Society. All rights reserved.