Kinetics of acid-catalyzed O-atom transfer from a hydroperoxorhodium complex to organic and inorganic substrates.

Abstract

Oxygen atom transfer from (NH(3))(4)(H(2)O)RhOOH(2+) to organic and inorganic nucleophiles takes place according to the rate law -d[(NH(3))(4)(H(2)O)RhOOH(2+)]/dt = k[H(+)] [(NH(3))(4)(H(2)O)RhOOH(2+)][nucleophile] for all the cases examined. The third-order rate constants were determined in aqueous solutions at 25 degrees C for (CH(2))(5)S (k = 430 M(-)(2) s(-)(1), micro = 0.10 M), (CH(2))(4)S(2) (182, micro = 0.10 M), CH(3)CH(2)SH (8.0, micro = 0.20 M), (en)(2)Co(SCH(2)CH(2)NH(2))(2+) (711, micro = 0.20 M), and, in acetonitrile-water, CH(3)SPh (130, 10% AN, micro = 0.20 M), PPh(3) (3.74 x 10(3), 50% AN), and (2-C(3)H(7))(2)S (45, 50% AN, micro = 0.20 M). Oxidation of PPh(3) by (NH(3))(4)(H(2)O)Rh(18)O(18)OH(2+) produced (18)OPPh(3). The reaction with a series of p-substituted triphenylphosphines yielded a linear Hammett relationship with rho = -0.53. Nitrous acid (k = 891 M(-)(2) s(-)(1)) is less reactive than the more nucleophilic nitrite ion (k = 1.54 x 10(4) M(-)(2) s(-)(1)).