Kinetics and mechanism of the reaction between mercury(II) and a series of macrocyclic organochromium cations

Kinetic data are presented for the reaction of alkylchromium complexes (H2O)([14]aneN(4))CrR2+ ([14]aneN(4) = 1,4,8,11-tetraazacyclotetradecane) with Hg2+ via electrophilic substitution. The rate constants decrease in the order CH3 (1.1 x 10(6) mol(-1) dm(3) s(-1)) > C2H5 (7.7 x 10(2)) > C3H7 (59) > 2-C3H7 (0.12) > CH2C(CH3)(3) (0.0086). A series of meta and para substituted benzyl complexes obey a Hammett relationship with the reaction constant rho = -1.66, consistent with electrophilic substitution at alpha -carbon.