Top Organomet Chem (2016) 56: 67–90
DOI: 10.1007/3418_2015_138
# Springer International Publishing Switzerland 2015
Published online: 26 July 2015
The Effects of Ancillary Ligands on
Metal–Carbon Bond Strengths as
Determined by C–H Activation
William D. Jones
Abstract The activation of C–H bonds by oxidative addition in about 30 different
substrates has been examined with three closely related metal species, [Tp
0 RhL],
where L ¼ CNneopentyl, PMe 3 , and P(OMe) 3 . Kinetic studies of the reductive
elimination of R–H provided data to ascertain the relative metal–carbon bond
strengths for a wide range of compounds. Trends in these bond strengths reveal
that there are two classes of C–H substrates: parent hydrocarbons and substituted
methanes. DFT calculations are used to support the observed trends, and some
generalizations are made by comparison to other metal systems.
Keywords Bond strengths Á Kinetics Á Oxidative addition Á Reductive elimination Á
Rhodium Á Thermodynamics
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
2 Hydrocarbon Activation by [Tp
0 Rh(CNR)] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh(CNR)(R)H 72
4 Hydrocarbon Activation by [Tp
0 Rh(PMe 3 )] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh(PMe 3 )(R)H 80
6 Hydrocarbon Activation by [Tp
0 Rh(P(OMe) 3 )] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh[P(OMe) 3 ]
(R)H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
W.D. Jones (*)
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
e-mail: jones@chem.rochester.edu
DOI: 10.1007/3418_2015_138
# Springer International Publishing Switzerland 2015
Published online: 26 July 2015
The Effects of Ancillary Ligands on
Metal–Carbon Bond Strengths as
Determined by C–H Activation
William D. Jones
Abstract The activation of C–H bonds by oxidative addition in about 30 different
substrates has been examined with three closely related metal species, [Tp
0 RhL],
where L ¼ CNneopentyl, PMe 3 , and P(OMe) 3 . Kinetic studies of the reductive
elimination of R–H provided data to ascertain the relative metal–carbon bond
strengths for a wide range of compounds. Trends in these bond strengths reveal
that there are two classes of C–H substrates: parent hydrocarbons and substituted
methanes. DFT calculations are used to support the observed trends, and some
generalizations are made by comparison to other metal systems.
Keywords Bond strengths Á Kinetics Á Oxidative addition Á Reductive elimination Á
Rhodium Á Thermodynamics
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
2 Hydrocarbon Activation by [Tp
0 Rh(CNR)] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh(CNR)(R)H 72
4 Hydrocarbon Activation by [Tp
0 Rh(PMe 3 )] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh(PMe 3 )(R)H 80
6 Hydrocarbon Activation by [Tp
0 Rh(P(OMe) 3 )] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7 Thermodynamic Determination of Rhodium–Carbon Bond Strengths in Tp
0 Rh[P(OMe) 3 ]
(R)H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
W.D. Jones (*)
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
e-mail: jones@chem.rochester.edu