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Title: CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I)

Abstract

The rhodium dicarbonyl {PhB(Ox Me2) 2Im Mes}Rh(CO) 2 (1) and primary silanes react by oxidative addition of a nonpolar Si–H bond and, uniquely, a thermal dissociation of CO. These reactions are reversible, and kinetic measurements model the approach to equilibrium. Thus, 1 and RSiH 3 react by oxidative addition at room temperature in the dark, even in CO-saturated solutions. The oxidative addition reaction is first-order in both 1 and RSiH 3, with rate constants for oxidative addition of PhSiH 3 and PhSiD 3 revealing k H/ k D ~ 1. The reverse reaction, reductive elimination of Si–H from {PhB(Ox Me2) 2Im Mes}RhH(SiH 2R)CO (2), is also first-order in [2] and depends on [CO]. The equilibrium concentrations, determined over a 30 °C temperature range, provide Δ H° = –5.5 ± 0.2 kcal/mol and Δ S° = –16 ± 1 cal·mol –1K –1 (for 1 ⇌ 2). The rate laws and activation parameters for oxidative addition (Δ H = 11 ± 1 kcal·mol –1 and Δ S = –26 ± 3 cal·mol –1·K –1) and reductive elimination (Δ H = 17 ± 1 kcal·mol –1 and Δ S = –10 ± 3 cal·mol –1K –1), particularly the negativemore » activation entropy for both forward and reverse reactions, suggest the transition state of the rate-determining step contains {PhB(Ox Me2) 2Im Mes}Rh(CO) 2 and RSiH 3. Comparison of a series of primary silanes reveals that oxidative addition of arylsilanes is ca. 5× faster than alkylsilanes, whereas reductive elimination of Rh–Si/Rh–H from alkylsilyl and arylsilyl rhodium(III) occurs with similar rate constants. Furthermore, the equilibrium constant K e for oxidative addition of arylsilanes is >1, whereas reductive elimination is favored for alkylsilanes.« less

Authors:
 [1];  [2]; ORCiD logo [1]
  1. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1502873
Report Number(s):
IS-J-9829
Journal ID: ISSN 0020-1669
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 6; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Biswas, Abhranil, Ellern, Arkady, and Sadow, Aaron D. CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I). United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.8b03425.
Biswas, Abhranil, Ellern, Arkady, & Sadow, Aaron D. CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I). United States. doi:10.1021/acs.inorgchem.8b03425.
Biswas, Abhranil, Ellern, Arkady, and Sadow, Aaron D. Fri . "CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I)". United States. doi:10.1021/acs.inorgchem.8b03425.
@article{osti_1502873,
title = {CO Displacement in an Oxidative Addition of Primary Silanes to Rhodium(I)},
author = {Biswas, Abhranil and Ellern, Arkady and Sadow, Aaron D.},
abstractNote = {The rhodium dicarbonyl {PhB(OxMe2)2ImMes}Rh(CO)2 (1) and primary silanes react by oxidative addition of a nonpolar Si–H bond and, uniquely, a thermal dissociation of CO. These reactions are reversible, and kinetic measurements model the approach to equilibrium. Thus, 1 and RSiH3 react by oxidative addition at room temperature in the dark, even in CO-saturated solutions. The oxidative addition reaction is first-order in both 1 and RSiH3, with rate constants for oxidative addition of PhSiH3 and PhSiD3 revealing kH/kD ~ 1. The reverse reaction, reductive elimination of Si–H from {PhB(OxMe2)2ImMes}RhH(SiH2R)CO (2), is also first-order in [2] and depends on [CO]. The equilibrium concentrations, determined over a 30 °C temperature range, provide ΔH° = –5.5 ± 0.2 kcal/mol and ΔS° = –16 ± 1 cal·mol–1K–1 (for 1 ⇌ 2). The rate laws and activation parameters for oxidative addition (ΔH‡ = 11 ± 1 kcal·mol–1 and ΔS‡ = –26 ± 3 cal·mol–1·K–1) and reductive elimination (ΔH‡ = 17 ± 1 kcal·mol–1 and ΔS‡ = –10 ± 3 cal·mol–1K–1), particularly the negative activation entropy for both forward and reverse reactions, suggest the transition state of the rate-determining step contains {PhB(OxMe2)2ImMes}Rh(CO)2 and RSiH3. Comparison of a series of primary silanes reveals that oxidative addition of arylsilanes is ca. 5× faster than alkylsilanes, whereas reductive elimination of Rh–Si/Rh–H from alkylsilyl and arylsilyl rhodium(III) occurs with similar rate constants. Furthermore, the equilibrium constant Ke for oxidative addition of arylsilanes is >1, whereas reductive elimination is favored for alkylsilanes.},
doi = {10.1021/acs.inorgchem.8b03425},
journal = {Inorganic Chemistry},
number = 6,
volume = 58,
place = {United States},
year = {2019},
month = {3}
}

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This content will become publicly available on March 1, 2020
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