Kinetics of water proton exchange of pentaqua(cyanomethyl)chromium(2+) in aqueous acid

The solvent water proton transverse (R 2 ) and longitudinal (R 1 ) relaxation rates have been studied for solutions of the organochromium(III) complex (H 2 O) 5 Cr(CH 2 CN) 2+ as a function of H + concentration (0.01-0.22 M) and temperature (5-70 o C). The temperature dependence of R 2 is typical of a chemical exchange process which is assigned to exchange of coordinated water protons because of the similarity to the behavior of Cr(OH 2 ) 6 3+ and (H 2 O) 5 Cr(N 3 ) 2+ .