The rates of reaction of (P(C6H11)3)2W(CO)3(L) (L = H2, D2, and N2) with pyridine have been studied by stopped-flow kinetics. The molecular nitrogen system shows simple first-order loss of N2 with a rate constant of 75 s-1 at 25°C and an activation energy of 17.8 ± 0.7 kcal/mol. The rate of reaction of the intermediate (P(C6H11)3)2W(CO)3 with N2 gas is 5.0 ± 1.0 × 105 M-1 s-1 at 25°C in toluene solution. Reactions of the hydrogen and deuterium complexes are complicated due to the presence of both molecular hydrogen (deuterium) and dihydride (dideuteride) complexes. These data are resolved and interpreted in terms of a rapid loss of molecular hydrogen (k = 469 s-1 for H2 and 267 s-1 for D2 at 25°C, ΔH‡ = 16.9 ± 2.2 kcal/mol for H2 and 16.2 ± 1.1 kcal/mol for D2). The hydride complex, which is present in ∼30%, reacts an order of magnitude slower than the molecular hydrogen complex (k = 37 s-1 for H2 and 33 s-1 for D2 at 25°C), ΔH‡ = 14.4 ± 0.5 kcal/mol for H2 and 14.7 ± 0.8 kcal/mol for D2). The rate of addition of H2 to (P(C6H11)3)2W(CO)3 is calculated to be 2.2 ± 0.3 × 106 M-1 s-1 at 25°C. These data are combined with earlier thermodynamic measurements to generate a reaction profile for binding and oxidative addition of hydrogen to the complex (P(C6H11)3)2W(CO)3.
ASJC Scopus subject areas
- Colloid and Surface Chemistry