WEAK RH[-H-C INTERACTIONS - MOLECULAR-STRUCTURE OF [TRANS-RH(CO)(8-METHYLQUINOLINE)(PPH3)2]BF4

Treatment of [Rh(CO)Cl(ER3)2] with the appropriate silver salt AgX in CH3CN affords the solvento complexes [trans-Rh(CO)(CH3CN)(ER3)2]X (4a, E = P, R = Ph, X = BF4; 4b, E = P, R = Cy, X = CF3SO3; 4c, E = As, R = Ph, X = BF4). Only 4a and 4c react at room temperature with 8-methylquinoline (mqH) to give the stable cationic complexes [trans-Rh(CO)(mqH)(EPh3)2]BF4 (5a, E = P; 5b, E = As). NMR characterization of 5 in solution suggests the presence of a quinoline methyl group weakly interacting with the rhodium center. The X-ray crystal structure determination of 5a confirmed the presence of a quinoline molecule coordinated through the N atom with the methyl group lying above the coordination plane. 5a crystallizes in the triclinic system, space group P1BAR, with a = 2.348 (2) angstrom, b = 14.424 (3) angstrom, c = 15.545 (3) angstrom, alpha = 77.36 (2)-degrees, beta = 81.22 (2)-degrees, gamma = 89.28 (2)-degrees, and Z = 2. The Rh...C(11) separation (3.118 angstrom) and Rh...H(11a) separation (ca. 2.21 angstrom) are in agreement with weak M...H-C interactions.