PHOSPHINE SUBSTITUTION IN n5-CYCLOPENTADIENYL-BIS-TRIPHENYLPHOSPHINECOBALT (I): EVIDENCE FOR A DISSOCIATIVE MECHANISM

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The substitution of trimethylphosphine for triphenylphosphine in {eta}{sup 5}-cyclopentadienyl-bis-triphenylphosphinecobalt(I), 1, to form {eta}{sup 5}-cyclopentadienyltrimethylphosphinetriphenylphosphinecobalt(I) was studied at -60°C in an NMR spectrometer. Kinetic measurements show the process to be first order in 1 and zero order in PMe{sub 3}; added PPh{sub 3} strongly inhibits the reaction rate. This information indicates the reaction proceeds by rapid reversible phosphine dissociation through the unsaturated CpCo(PPh{sub 3}) intermediate. The rate for generation of that intermediate, k{sub 1}, is 1.15 x 10{sup -3} sec{sup -1} while the ratio of rate constant k{sub 2} (for conversion of intermediate to products) to k{sub -1} (return to starting ... continued below

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Janowicz, Andrew H.; Bryndza, Henry E. & Bergman, Robert G. June 1, 1980.

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The substitution of trimethylphosphine for triphenylphosphine in {eta}{sup 5}-cyclopentadienyl-bis-triphenylphosphinecobalt(I), 1, to form {eta}{sup 5}-cyclopentadienyltrimethylphosphinetriphenylphosphinecobalt(I) was studied at -60°C in an NMR spectrometer. Kinetic measurements show the process to be first order in 1 and zero order in PMe{sub 3}; added PPh{sub 3} strongly inhibits the reaction rate. This information indicates the reaction proceeds by rapid reversible phosphine dissociation through the unsaturated CpCo(PPh{sub 3}) intermediate. The rate for generation of that intermediate, k{sub 1}, is 1.15 x 10{sup -3} sec{sup -1} while the ratio of rate constant k{sub 2} (for conversion of intermediate to products) to k{sub -1} (return to starting materials) is 4 at -60°C. Possible structures for CpCo(L) are discussed in light of recent indications that the linear structure has an open-shell electronic configuration.

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  • Journal Name: Journal of the America Chemical Society

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  • Report No.: LBL-11160
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 1076514
  • Archival Resource Key: ark:/67531/metadc831123

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  • June 1, 1980

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  • May 19, 2016, 9:45 a.m.

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  • June 16, 2016, 5:14 p.m.

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Janowicz, Andrew H.; Bryndza, Henry E. & Bergman, Robert G. PHOSPHINE SUBSTITUTION IN n5-CYCLOPENTADIENYL-BIS-TRIPHENYLPHOSPHINECOBALT (I): EVIDENCE FOR A DISSOCIATIVE MECHANISM, article, June 1, 1980; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc831123/: accessed September 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.