Octahedral metal carbonyls. : XXXVII. the kinetics and mechanism of reactions of amines with the group VI-B metal carbonyls

✍ Scribed by J.E. Pardue; G.R. Dobson

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 503 KB
• Volume: 20
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)94117-3

✦ Synopsis

Studies of the rates of reaction of the Group VI-B metal hexacarbonyls (M = 0, MO, W) with benzylamine, cyclohexylamine and aniline (amine) support a rate law, -d[M(COj6f/dt = kIIM(CO)ej + k2/M(C0)e]famineJ. The rate law is suggestive of two competing mechanisms, with the amine-independent path involving rate-determining dissociation of CO followed by amine uptake (0). The remarkable parallelism in rates for the competing processes for all three metals suggests the same factors to influence the rate of reaction by each path. Activation parameters for reaction of Mo(CO), with benzylamine, and the relative insensitivity of the rate to the iden thy of a wide variety of incoming nucleophiles for the amine-dependent path support a mechanism (/a), in which M-CO bond breaking is very important. Comparisons of second-order rate constants for reactions of amines, and phosphines and phosphites indicate relatively little n-interaction in the transition state for substitution reactions of the latter.