The substitution of CO in Ni(CO)₄ by another molecule L [where L is an electron-pair donor such as P(CH₃)₃] was studied some years ago and led to an understanding of some of the general principles that govern the chemistry of compounds having metal–CO bonds. (See J. P. Day, F. Basolo, and R. G. Pearson: Journal of the American Chemical Society, Vol. 90, p. 6927, 1968.) A detailed study of the kinetics of the reaction led to the following mechanism:(a) What is the molecularity of each of the elementary reactions?
(b) Doubling the concentration of Ni(CO)₄increased the reaction rate by a factor of 2. Doubling the concentration of L had no effect on the reaction rate. Based on this information, write the rate equation for the reaction. Does this agree with the mechanism described?
(c) The experimental rate constant for the reaction, when L = P(C₆H₅)₃, is 9.3 × 10⁻³ s⁻¹ at 20°C. If the initial concentration of Ni(CO)₄ is 0.025 M, what is the concentration of the product after 5.0 minutes?

Transcribed Image Text:

Slow: Fast: Ni(CO)4 Ni(CO)3 + CO Ni(CO)3 + L→ Ni(CO)3L