Photochemically generated transients from κ 2- and κ 3-Triphos derivatives of group 6 metal carbonyls and their reactivity with olefins

Samuel J. Kyran, Muhammad Sohail, Matthew Knestrick, Ashfaq A. Bengali, Donald J. Darensbourg

Research output: Contribution to journalArticle

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Abstract

The synthesis and characterization of (κ 2-Triphos)M(CO) 4 derivatives, where M = Mo, W and Triphos = MeC(CH 2PPh 2) 3, are reported. Photolyses of these metal carbonyls in dichloromethane or CO 2-saturated dichloromethane readily afford the (κ 3-Triphos)M(CO) 3 complexes with no evidence of significant solvent or carbon dioxide interactions with the site vacated by CO. However, in the presence of 1-hexene a transient (κ 2-Triphos)M(CO) 3(1-hexene) adduct was observed, which subsequently releases the olefin with formation of the stable κ 3-tricarbonyl species. In the case of M = W the kinetic parameters for this process were assessed, with the rate of olefin replacement being inversely proportional to [1-hexene]. A dissociative rate constant of 25.6 ± 1.1 s -1 at 298 K was determined for olefin loss, with the selectivity for 1-hexene vs free phosphine arm addition to the unsaturated intermediate being somewhat surprisingly large at 22. The activation parameters measured were δH = 26.1 ± 0.4 kcal/mol and δS = 36 ± 3 eu, which are consistent with a dissociative substitution reaction. The kinetic parameters for this transformation were unaffected in the presence of excess quantities of CO 2. Although no interaction of CO 2 with the transient species resulting from CO loss in the κ 2 complex was noted on the time scale of 50 ms, an intermediate described as an η 2- HSiEt 3 complex was observed upon addition of triethylsilane. This latter transient species underwent dissociation with κ 3-complex formation about 15 times as fast as its 1-hexene analogue. X-ray structures of the κ 2 complexes of Mo and W where the dangling phosphine arm has undergone oxidation are also reported.

Original languageEnglish
Pages (from-to)3163-3170
Number of pages8
JournalOrganometallics
Volume31
Issue number8
DOIs
Publication statusPublished - 23 Apr 2012

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hexenes
Alkenes
Carbon Monoxide
alkenes
reactivity
Metals
Derivatives
phosphine
metals
phosphines
Methylene Chloride
Kinetic parameters
kinetics
dioxides
adducts
photolysis
carbon dioxide
selectivity
interactions
activation

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Photochemically generated transients from κ 2- and κ 3-Triphos derivatives of group 6 metal carbonyls and their reactivity with olefins. / Kyran, Samuel J.; Sohail, Muhammad; Knestrick, Matthew; Bengali, Ashfaq A.; Darensbourg, Donald J.

In: Organometallics, Vol. 31, No. 8, 23.04.2012, p. 3163-3170.

Research output: Contribution to journalArticle

Kyran, Samuel J. ; Sohail, Muhammad ; Knestrick, Matthew ; Bengali, Ashfaq A. ; Darensbourg, Donald J. / Photochemically generated transients from κ 2- and κ 3-Triphos derivatives of group 6 metal carbonyls and their reactivity with olefins. In: Organometallics. 2012 ; Vol. 31, No. 8. pp. 3163-3170.
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abstract = "The synthesis and characterization of (κ 2-Triphos)M(CO) 4 derivatives, where M = Mo, W and Triphos = MeC(CH 2PPh 2) 3, are reported. Photolyses of these metal carbonyls in dichloromethane or CO 2-saturated dichloromethane readily afford the (κ 3-Triphos)M(CO) 3 complexes with no evidence of significant solvent or carbon dioxide interactions with the site vacated by CO. However, in the presence of 1-hexene a transient (κ 2-Triphos)M(CO) 3(1-hexene) adduct was observed, which subsequently releases the olefin with formation of the stable κ 3-tricarbonyl species. In the case of M = W the kinetic parameters for this process were assessed, with the rate of olefin replacement being inversely proportional to [1-hexene]. A dissociative rate constant of 25.6 ± 1.1 s -1 at 298 K was determined for olefin loss, with the selectivity for 1-hexene vs free phosphine arm addition to the unsaturated intermediate being somewhat surprisingly large at 22. The activation parameters measured were δH † = 26.1 ± 0.4 kcal/mol and δS † = 36 ± 3 eu, which are consistent with a dissociative substitution reaction. The kinetic parameters for this transformation were unaffected in the presence of excess quantities of CO 2. Although no interaction of CO 2 with the transient species resulting from CO loss in the κ 2 complex was noted on the time scale of 50 ms, an intermediate described as an η 2- HSiEt 3 complex was observed upon addition of triethylsilane. This latter transient species underwent dissociation with κ 3-complex formation about 15 times as fast as its 1-hexene analogue. X-ray structures of the κ 2 complexes of Mo and W where the dangling phosphine arm has undergone oxidation are also reported.",
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N2 - The synthesis and characterization of (κ 2-Triphos)M(CO) 4 derivatives, where M = Mo, W and Triphos = MeC(CH 2PPh 2) 3, are reported. Photolyses of these metal carbonyls in dichloromethane or CO 2-saturated dichloromethane readily afford the (κ 3-Triphos)M(CO) 3 complexes with no evidence of significant solvent or carbon dioxide interactions with the site vacated by CO. However, in the presence of 1-hexene a transient (κ 2-Triphos)M(CO) 3(1-hexene) adduct was observed, which subsequently releases the olefin with formation of the stable κ 3-tricarbonyl species. In the case of M = W the kinetic parameters for this process were assessed, with the rate of olefin replacement being inversely proportional to [1-hexene]. A dissociative rate constant of 25.6 ± 1.1 s -1 at 298 K was determined for olefin loss, with the selectivity for 1-hexene vs free phosphine arm addition to the unsaturated intermediate being somewhat surprisingly large at 22. The activation parameters measured were δH † = 26.1 ± 0.4 kcal/mol and δS † = 36 ± 3 eu, which are consistent with a dissociative substitution reaction. The kinetic parameters for this transformation were unaffected in the presence of excess quantities of CO 2. Although no interaction of CO 2 with the transient species resulting from CO loss in the κ 2 complex was noted on the time scale of 50 ms, an intermediate described as an η 2- HSiEt 3 complex was observed upon addition of triethylsilane. This latter transient species underwent dissociation with κ 3-complex formation about 15 times as fast as its 1-hexene analogue. X-ray structures of the κ 2 complexes of Mo and W where the dangling phosphine arm has undergone oxidation are also reported.

AB - The synthesis and characterization of (κ 2-Triphos)M(CO) 4 derivatives, where M = Mo, W and Triphos = MeC(CH 2PPh 2) 3, are reported. Photolyses of these metal carbonyls in dichloromethane or CO 2-saturated dichloromethane readily afford the (κ 3-Triphos)M(CO) 3 complexes with no evidence of significant solvent or carbon dioxide interactions with the site vacated by CO. However, in the presence of 1-hexene a transient (κ 2-Triphos)M(CO) 3(1-hexene) adduct was observed, which subsequently releases the olefin with formation of the stable κ 3-tricarbonyl species. In the case of M = W the kinetic parameters for this process were assessed, with the rate of olefin replacement being inversely proportional to [1-hexene]. A dissociative rate constant of 25.6 ± 1.1 s -1 at 298 K was determined for olefin loss, with the selectivity for 1-hexene vs free phosphine arm addition to the unsaturated intermediate being somewhat surprisingly large at 22. The activation parameters measured were δH † = 26.1 ± 0.4 kcal/mol and δS † = 36 ± 3 eu, which are consistent with a dissociative substitution reaction. The kinetic parameters for this transformation were unaffected in the presence of excess quantities of CO 2. Although no interaction of CO 2 with the transient species resulting from CO loss in the κ 2 complex was noted on the time scale of 50 ms, an intermediate described as an η 2- HSiEt 3 complex was observed upon addition of triethylsilane. This latter transient species underwent dissociation with κ 3-complex formation about 15 times as fast as its 1-hexene analogue. X-ray structures of the κ 2 complexes of Mo and W where the dangling phosphine arm has undergone oxidation are also reported.

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