DISPLACEMENT KINETICS OF 1,5-CYCLOOCTADIENE FROM MO(CO)4(ETA(2-2)-1,5-CYCLOOCTADIENE) BY BIS(DIPHENYLPHOSPHINO)METHANE

Citation
A. Tekkaya et al., DISPLACEMENT KINETICS OF 1,5-CYCLOOCTADIENE FROM MO(CO)4(ETA(2-2)-1,5-CYCLOOCTADIENE) BY BIS(DIPHENYLPHOSPHINO)METHANE, Inorganic chemistry, 33(11), 1994, pp. 2439-2443
Citations number
38
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
ISSN journal
00201669
Volume
33
Issue
11
Year of publication
1994
Pages
2439 - 2443
Database
ISI
SICI code
0020-1669(1994)33:11<2439:DKO1FM>2.0.ZU;2-A
Abstract
The kinetics of the thermal substitution of 1,5-cyclooctadiene (COD) f rom [Mo(CO)4(eta2:2-COD)] (1) by bis-(diphenylphosphino)methane (DPPM) and the formation of [Mo(CO)4(DPPM)] (6) was studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of 1, and the observed rate constant, k(obs), dep ends on the concentrations of both leaving COD and entering DPPM ligan d. From the evaluation of data collected, one can propose a mechanism in which the rate-determining step is the cleavage of one of two Mo-ol efin bonds. A rate law is derived from the proposed mechanism. The eva luation of the kinetic data gives the enthalpy of activation DELTAH = 80 (+/-1) kJ.mol-1 and the entropy of activation DELTAS = -55 (+/-2) J.mol-1.K-1. The negative entropy value obtained tends to suggest an associative mechanism in transition states. Material balance and yield of product do not show any significant depletion implying that there is no decomposition in noticeable amounts during the substitution reac tion.