| Abstrakt: |
The reactivity of the previously (Organometallics 2000, 19, 824−833) prepared hydride complexes (C5H4CO2H)L(CO)2WH (L = CO, PMe3) and the corresponding metal−metal dimers [(C5H4CO2H)L(CO)2W]2 in pulse radiolysis studies in aqueous solution is reported. The disappearance of eaq- was monitored to determine the rate constants for one-electron reduction. The smallest reduction rate constant was obtained for the dianion (C5H4CO2)(CO)3W2- (4.3 × 109 M-1 s-1), and the largest value (1.2 × 1010 M-1 s-1) was observed for its conjugate acid (C5H4CO2)(CO)3WH-. For the PMe3-substituted complexes, the dimer reduction rate constant was about twice as large as that for the hydride (k = 8.4 × 109 M-1 s-1). Rate constants for reaction with CO2-, 3.2 × 108 (pH 5) and 3.0 × 107 (pH 9.7) M-1 s-1, were determined for (C5H4CO2)(CO)3WH- and (C5H4CO2)(PMe3)(CO)2WH-, respectively. Rate constants for the reactions of the hydride complexes with the carbon-centered radical from tert-butyl alcohol and the α-hydroxy radicals from ethanol and 2-propanol radicals were in the ranges (0.9−4.8) × 108 and (0.3−0.6) × 108 M-1 s-1 for (C5H4CO2)(CO)3WH- and (C5H4CO2)(PMe3)(CO)2WH-, respectively. The transient produced in all of these reactions was the metal radical, which was observed to dimerize with k = 2.4 × 109 and 2.2 × 108 M-1 s-1 for (C5H4CO2)(CO)3WH- and (C5H4CO2)(PMe3)(CO)2WH-, respectively. |
