CRYSTAL-STRUCTURE OF (METHYL 2-(METHYLAMINO)-1-CYCLOPENTENE-1-DITHIOCARBOXYLATO-KAPPA-N,KAPPA-S)-CARBONYL(TRIPHENYLPHOSPHINE)RHODIUM(I) AND KINETICS OF IODOMETHANE OXIDATIVE ADDITION

The preparation of the title complex, (methyl 2-(methylamino)-1-cyclopentene-1-dithiocarboxylato)carbonyl(triphenylphosphine(rhodium(I), is described. This complex, C27H27NOS2OPRh, crystallizes in the monoclinic space group P2(1)/n, with a = 15.665 (2) angstrom, b = 9.685 (1) angstrom, c = 18.166 (2) angstrom, beta = 110.57 (1)-degrees, Z = 4, and rho(calc) = 1.491 g cm-3. A final R-value of 4.70% resulted from refinement of 4808 observed reflections. The title complex, in which triphenylphosphine is coordinated trans to the nitrogen atom of the methyl 2-(methylamino)-1-cyclopentene-1-dithiocarboxylato ligand (MACSM-), undergoes oxidative addition with iodomethane with the formation of an alkyl intermediate, followed by carbonyl insertion with the formation of the corresponding Rh(III)-acyl complex. The reaction proceeds via an associative equilibrium followed by the methyl migration to form the acyl species according to the reaction [GRAPHICS] At 25.5-degrees-C in CHCl3 the equilibrium and forward and reverse rate constants for the first reaction were determined as 5 (1) M-1, 3.4 (1) x 10(-2) M-1 s-1, and 8.6 (8) x 10(-3) s-1, and the limiting rate constant for the Rh(III)-acyl formation was determined as 8.1 (5) x 10(-3) s-1.