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


Kayran C., Kozanoglu F., Ozkar S., Saldamli S., Tekkaya A., Kreiter C.

INORGANICA CHIMICA ACTA, vol.284, no.2, pp.229-236, 1999 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 284 Issue: 2
  • Publication Date: 1999
  • Doi Number: 10.1016/s0020-1693(98)00293-x
  • Journal Name: INORGANICA CHIMICA ACTA
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.229-236
  • Keywords: ligand substitution, molybdenum complexes, tungsten complexes, diphosphine complexes, kinetics and mechanism, ISOKINETIC RELATIONSHIP, TETRACARBONYL

Abstract

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.