A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus

Ching, S; Shriver, D F

doi:10.1021/ja00191a022

Title: A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus

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Abstract

The kinetics of phosphine migration from a metal to carbon site in a trimetallic cluster have been investigated. The rate of ligand migration is significantly decreased by bulky phosphines and is relatively insensitive to changes in phosphine basicity. Bridging phosphine and carbonyl ligands are proposed for the transition state, and pairwise exchange of these ligands is favored. Activation parameters for PR{sub 3} = PEt{sub 3}, PEt{sub 2}Ph, and PMePh{sub 2} are {Delta}H{double dagger} = +16.8 to +17.3 kcal/mol and {Delta}S{double dagger} = {minus}17 to {minus}21 cal/mol K. Reactions of small phosphines (P(OMe){sub 3}, PMe{sub 3}, and PMe{sub 2}Ph) contain an additional term in the rate law due to phosphine substitution for CO in (PPN)(Fe{sub 2}Co(CO){sub 8}(PR{sub 3})(CCO)), which gives (PPN)(Fe{sub 2}Co(CO){sub 8}(PR{sub 3})(CPR{sub 3})). This reaction is in competition with ligand migration. Competition experiments and the observed steric barrier to substitution lead to the proposal that two phosphine ligands initially coordinate to the Co metal center and this is followed by a rapid intramolecular migration of one phosphine to the capping carbon atom. In the course of these mechanistic studies (PPN)(Fe{sub 2}Co(CO){sub 8}(PMe{sub 3})(CPMe{sub 3})) has been isolated and characterized.

Authors:

Ching, S; Shriver, D F ^[1]

Northwestern Univ., Evanston, IL (USA)

Publication Date:: Wed Apr 26 00:00:00 EDT 1989

OSTI Identifier:: 5119462

Resource Type:: Journal Article

Journal Name:: Journal of the American Chemical Society; (USA)

Additional Journal Information:: Journal Volume: 111:9; Journal ID: ISSN 0002-7863

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBONYLS; CHEMICAL REACTIONS; IRON COMPLEXES; PHOSPHINES; ACTIVATION ENERGY; CHEMICAL REACTION KINETICS; EXPERIMENTAL DATA; LIGANDS; PH VALUE; THERMODYNAMICS; COMPLEXES; DATA; ENERGY; INFORMATION; KINETICS; NUMERICAL DATA; PHOSPHORUS COMPOUNDS; REACTION KINETICS; TRANSITION ELEMENT COMPLEXES; 400201* - Chemical & Physicochemical Properties

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                    Ching, S, and Shriver, D F. A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus.  United States: N. p., 1989. 
        Web.  doi:10.1021/ja00191a022.

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                    Ching, S, & Shriver, D F. A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus.  United States.  https://doi.org/10.1021/ja00191a022

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                    Ching, S, and Shriver, D F. 1989.  
        "A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus".  United States.  https://doi.org/10.1021/ja00191a022.

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@article{osti_5119462,

  title        = {A mechanistic investigation of phosphine migration and substitution in (Fe sub 2 Co(CO) sub 8 (PR sub 3 )(CCO)) sup minus},

  author       = {Ching, S and Shriver, D F},

  abstractNote = {The kinetics of phosphine migration from a metal to carbon site in a trimetallic cluster have been investigated. The rate of ligand migration is significantly decreased by bulky phosphines and is relatively insensitive to changes in phosphine basicity. Bridging phosphine and carbonyl ligands are proposed for the transition state, and pairwise exchange of these ligands is favored. Activation parameters for PR{sub 3} = PEt{sub 3}, PEt{sub 2}Ph, and PMePh{sub 2} are {Delta}H{double dagger} = +16.8 to +17.3 kcal/mol and {Delta}S{double dagger} = {minus}17 to {minus}21 cal/mol K. Reactions of small phosphines (P(OMe){sub 3}, PMe{sub 3}, and PMe{sub 2}Ph) contain an additional term in the rate law due to phosphine substitution for CO in (PPN)(Fe{sub 2}Co(CO){sub 8}(PR{sub 3})(CCO)), which gives (PPN)(Fe{sub 2}Co(CO){sub 8}(PR{sub 3})(CPR{sub 3})). This reaction is in competition with ligand migration. Competition experiments and the observed steric barrier to substitution lead to the proposal that two phosphine ligands initially coordinate to the Co metal center and this is followed by a rapid intramolecular migration of one phosphine to the capping carbon atom. In the course of these mechanistic studies (PPN)(Fe{sub 2}Co(CO){sub 8}(PMe{sub 3})(CPMe{sub 3})) has been isolated and characterized.},

  doi          = {10.1021/ja00191a022},

  url          = {https://www.osti.gov/biblio/5119462},
  journal      = {Journal of the American Chemical Society; (USA)},

  issn         = {0002-7863},

  number       = ,

  volume       = 111:9,

  place        = {United States},

  year         = {Wed Apr 26 00:00:00 EDT 1989},

  month        = {Wed Apr 26 00:00:00 EDT 1989}

}

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