The kinetics of the epoxidation of cis-cyclooctene, 2-norbornene and limonene catalyzed by cis-[RuCl2(dppb)(2',2'-bipy)] (1) or trans-[RuCl2(dppb)(2,2'-bipy)] (2) (where, dppb: 1,4-bis(diphenylphosphino)butane; 2,2'-bipy: 2,2'-bipyridine) in the presence of iodosylbenzene (PhIO) follow a Michaelis-Menten type mechanism. The performance of I and 2 in the epoxidation of cis-cyclooctene, 2-norbornene and limonene are respectively (1) V-max = 8.62,11.6 and 4.98 mol 1(-1) min(-1) and (2) V-max = 4.28, 7.55 and 5.66 mol 1(-1) min(-1). The activation energies of the epoxidations catalyzed by 1 are 1.5-3.3 kcal mol(-1) lower than those measured for 2. (C) 2003 Elsevier B.V. All rights reserved.