Publication Date

3-1-2019

Department

Ames Laboratory; Chemistry

Campus Units

Ames Laboratory, Chemistry

OSTI ID+

1502873

Report Number

IS-J 9829

DOI

10.1021/acs.inorgchem.8b03425

Journal Title

Inorganic Chemistry

Volume Number

58

Issue Number

6

First Page

3815

Last Page

3824

Abstract

The rhodium dicarbonyl {PhB(Ox(Me2))(2)Im(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 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 k(H)/k(D) similar to 1. The reverse reaction, reductive elimination of Si-H from {PhB(Ox(Me2))(2)Im(Mes)}RhH(SiH2R)CO (2), is also first-order in [2] and depends on [CO]. The equilibrium concentrations, determined over a 30 degrees C temperature range, provide AH =-5.5 0.2 kcal/mol and AS =-16 1 cal"mo1-11C-1 (for 1 t 2). The rate laws and activation parameters for oxidative addition (OH* = 11 1 kcal-morl and AS* = -26 3 cal"mo1-1"K-1) and reductive elimination (OH* = 17 1 kcal-mol' and AS* =-10 3 cal-mol(-1)K(-1)), particularly the negative activation entropy for both forward and reverse reactions, suggest the transition state of the rate-determining step contains {PhB(Ox(Mes))(2)/mMes}Rh(CO)(2) and RSiH3. Comparison of a series of primary silanes reveals that oxidative addition of arylsilanes is ca. 5x faster than alkylsilanes, whereas reductive elimination of Rh-Si/Rh-H from alkylsilyl and arylsilyl rhodium(III) occurs with similar rate constants. Thus, the equilibrium constant Ke for oxidative addition of arylsilanes is >1, whereas reductive elimination is favored for alkylsilanes.

DOE Contract Number(s)

AC02-07CH11358

Language

en

Department of Energy Subject Categories

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Sunday, March 01, 2020

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