KINETICS OF ACETYL RADICAL FORMATION FROM METHYL RADICALS AND CARBON-MONOXIDE AND CRYSTAL-STRUCTURES OF 2 ACETYLCOBALT COMPLEXES

Methyl radicals react with macrocyclic cobalt complexes (H2O)2LCo2+ (L1 = 1,4,8,11-tetraazacyclotetradecane, L2 = C-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)in the presence of CO in acidic aqueous solution. The reaction yields a mixture of methyl and acetyl complexes as a result of the competition between CO and (H2O)2CoL2+ for CH3.. Kinetic competition experiments yielded the rate constant for the capture of CH3. by CO, k(CO) = (2.0 +/- 0.3) X 10(6) M-1 s-1. The acetyl complex of CoL1 crystallizes with either H2O or ClO4-coordinated trans to the acetyl group. Both the red [(ClO4)L1CoC(O)CH3](ClO4) (1) and the yellow [(H2O)L1-CoC(O)CH3](ClO4)2.H2O (2) crystallize in the centric space group P2(1)/c with four molecules in a unit cell of dimensions a = 10.539 (1 ) angstrom, b = 12.548 (2) angstrom, c = 1 4.915 (2) angstrom, and beta = 93.74 (3)-degrees for 1 and a = 12.588 (3) angstrom, b = 8.821 (3) angstrom, c = 19.398 (5) angstrom, and beta = 96.34 (2)-degrees for 2. The data refined to final values of the unweighted R factors of 0.037 (1) and 0.054 (2).