PREPARATION AND KINETICS OF HYDROLYSIS OF PENTAAMMINEPERRHENATOCOBALT(3) ION

A well-defined compound containing coordinated ReO4- has been isolated by the dehydration of [Co(NH3)5OH2](ReO4)3· 2H2O under vacuum at 95-130°. In aqueous solution, [Co(NH3)5ReO4]X2 aquates at a measurable rate and follows the rate law: rate = (k0 + k[H+] + kOH[OH-]([Co(NH3)5bReCh42+]. The values k0 = (3.12 ± 0.44) × 10-4 sec-1, kH = 1.22 ± 0.03 M-1 sec-1, and kOH. = (2.89 ± 0.11) × 104 5M-1 sec-1 were obtained at 25° and µ = 0.004-0.12. Using O18 as a tracer, the formation in the solid state was found to occur by fission of the Co-O bond while hydrolysis in dilute H+ or OH-occurred by Re-O bond breaking. In the neutral region (pH 4-7) more complex oxygen-transfer behavior was observed. Hydrolysis was strongly catalyzed by HOAc, OAc-, and H(phthalate)-. © 1968, American Chemical Society. All rights reserved.