Mechanistic study of the reaction oḟCr(CO)3C5Me5 with H2S yielding HCr(CO)3C5Me5, HSCr(CO)3C5Me5, and C5Me5(CO)2Cr=S=Cr(CO)2C 5Me5.

Kenneth B. Capps, Andreas Bauer, Telvin D. Ju, Carl D. Hoff

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Reaction of a large excess of H2S with 2 mol of ̇Cr(CO)3C5Me5 yields HCr(CO)3C5Me5 and HSCr(CO)3C5Me5. Kinetic studies of this reaction show two reaction pathways are followed. At pressures of CO above 10-15 atm and temperatures ≤ 10°C, a third-order rate law d[P]/dt = k3rd order[̇Cr(CO)3C5Me5] 2[H2S] is followed. The value of the third-order rate constant 70 ± 5 M-2 s-1 is essentially independent of temperature in the range -30 to +10°C. As the pressure of CO is reduced, mixed-order kinetics is followed, and under argon atmosphere the reaction obeys the following second-order rate law: d[P]/dt = k2nd order[̇Cr(CO)3C5Me 3][H2S]. The value of k2nd order was found to be 0.20 ± 0.05 M-1 s-1 at 1°C and 0.30 ± 0.05 M-1 s-1 at 10°C. This reaction channel is proposed to proceed by rate-determining ligand substitution and formation of the hydrogen sulfide substituted radical complex ̇Cr(H2S)(CO)2C5Me5. The rate of ligand substitution of ̇Cr(CO)3C5Me5 by PMe2Ph yielding the phosphine-substituted radical ̇Cr(PMe2Ph)(CO)2C5Me5 has been reinvestigated and shown to have rate constants and activation parameters similar to those proposed for rate-determining formation of ̇Cr(H2S)(CO)2C5Me5. A reasonable fit to data at intermediate pressures of CO is obtained at T ≤ 10°C by combining the 17e- second order and 19e- third-order mechanisms for oxidative addition. The complex HSCr(CO)3C5Me5 can react with an additional 2 mol of ̇Cr(CO)3C5Me5 yielding HCr(CO)3C5Me5 + C5Me5(CO)2Cr=S=Cr(CO)2C 5Me5 + 2CO. At a temperature of 50°C under 1 atm of CO the net reaction 4̇Cr(CO)3C5Me5 + H2S → 2HCr(CO)3C5Me5 + C5Me5(CO)2Cr= S=Cr(CO)2C5Me5 + 2CO occurs within minutes without formation of detectable amounts of HSCr(CO)3C5Me5.

Original languageEnglish (US)
Pages (from-to)6130-6135
Number of pages6
JournalInorganic Chemistry
Volume38
Issue number26
DOIs
StatePublished - 1999

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Fingerprint Dive into the research topics of 'Mechanistic study of the reaction of<sup>̇</sup>Cr(CO)<sub>3</sub>C<sub>5</sub>Me<sub>5</sub> with H<sub>2</sub>S yielding HCr(CO)<sub>3</sub>C<sub>5</sub>Me<sub>5</sub>, HSCr(CO)<sub>3</sub>C<sub>5</sub>Me<sub>5</sub>, and C<sub>5</sub>Me<sub>5</sub>(CO)<sub>2</sub>Cr=S=Cr(CO)<sub>2</sub>C <sub>5</sub>Me<sub>5</sub>.'. Together they form a unique fingerprint.

  • Cite this