Ligand substitution kinetics in M(CO)(4)(eta(2 : 2)-1,5-cyclooctadiene) complexes (M = Cr, Mo, W) - substitution of 1,5-cyclooctadiene by bis(diphenylphosphino)alkanes

Date

1999-01-30

Author

Kayran, C
Kozanoglu, F
Özkar, Saim
Saldamli, S
Tekkaya, A
Kreiter, CG

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The thermal substitution kinetics of 1,5-cyclooctadiene (COD) by bis(diphenylphosphino)alkanes (PP), (C6H5)(2)P(CH2)(n)P(C6H5)(2) (n = 1, 2, 3) in M(CO)(4)(eta(2:2)-COD) complexes (M = Cr, Mo, W), were studied by quantitative FT-LR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of the leaving COD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism. the rate determining step is the cleavage of one metal-olefin bond of the COD ligand. A rate-law is derived from the proposed mechanism. The evaluation of the kinetic data gives the activation parameters which support an associative mechanism in the transition states. Both the observed rare constant and the activation parameters show little variation with the chain length of the diphosphine ligand. (C) 1999 Elsevier Science S.A. All rights reserved.

Subject Keywords

Ligand Substitution, Molybdenum Complexes, Tungsten Complexes, Diphosphine Complexes, Kinetics And Mechanism

URI

https://hdl.handle.net/11511/42687

Journal

INORGANICA CHIMICA ACTA

DOI

https://doi.org/10.1016/s0020-1693(98)00293-x

Collections

Department of Chemistry, Article

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DISPLACEMENT KINETICS OF 1,5-CYCLOOCTADIENE FROM MO(CO)4(ETA(2-2)-1,5-CYCLOOCTADIENE) BY BIS(DIPHENYLPHOSPHINO)METHANE TEKKAYA, A; KAYRAN, C; Özkar, Saim; KREITER, CG (American Chemical Society (ACS), 1994-05-25) The kinetics of the thermal substitution of 1,5-cyclooctadiene (COD) from [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), depends on the concentrations of both leaving COD and entering DPPM ligand. From the evaluation of data collected, one can propose a mechanism in which the rate-dete...
Displacement kinetics of 1,5-cyclooctadiene from M(CO)(4)(eta(2:2)-1.5-cyclooctadiene) (M=Cr, Mo, W) by bis(diphenylphosphino)alkane Kayran, C; Okan, E; Özkar, Saim; Ozturk, O; Saldamli, S; Tekkaya, A; Kreiter, CG (Walter de Gruyter GmbH, 1997-01-01) The thermal substitution kinetics of 1,5-cyclooctadiene (COD) from M(CO)(4)(eta(2:2)-COD) (M = Cr, Mo, W) by bis(diphenylphosphino)alkane, (C6H5)(2)P(CH2)(n)-P(C6H5)(2) (n = 1, 2, 3), was studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of starting complex and the observed rate constant depends on the concentrations of both the leaving COD and entering diphosphine ligand. In the proposed mechanism the rate determining step is the cleavage of ...
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