Activation of Carbon-Hydrogen Bonds via 1,2-Addition across M-X (X = OH or NH2) Bonds of d6 Transition Metals as a Potential Key Step in Hydrocarbon Functionalization: A Computational Study Page: 13,173
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Key Step in Hydrocarbon Functionalization ARTICLES
Scheme 1. Oxidative Addition (OA) and a-Bond Metathesis (SBM)
Mechanisms for C-H Bond Activation; q Denotes the Formal
Oxidation State of the Metal
I > LnMq+ H
In the typical OA mechanism, both the carbon and hydrogen
of the C-H bond that is cleaved are transferred to a low-valent
transition metal center via a three-centered transition state,
Scheme 1.11 In contrast to the three-center transition state
associated with OA, SBM is a concerted reaction involving four
atomic centers including the metal center, the ligand that receives
the transferred proton, and the C and H atoms of the bond being
activated, Scheme 1. The SBM pathway leaves the formal
oxidation state of the metal center unchanged. Cundari has
contrasted OA and SBM pathways of carbon-hydrogen bond
activation in terms of metal complex to substrate electron
donation and backdonation.12 Both OA and SBM are character-
ized by an "electrophilic" phase with dominant substrate to metal
donation early (i.e., before the transition state) in the reaction
coordinate. A "nucleophilic" phase dominated by metal complex
to substrate backdonation follows and serves to delineate the
mechanisms.12 In typical (i.e., monometallic complex) OA
pathways, the metal acts as both electrophile and nucleophile,
and thus both ends of the C-H bond being activated end up on
the metal. For SBM systems, the donor orbital on the metal
complex is a metal-ligand frontier orbital polarized toward the
more electronegative ligand. Periana and Goddard et al. have
proposed an oxidative-hydrogen migration (OHM) mechanism
for C-H activation by Ir(III) complexes as a variant of OA
and SBM.13 The OHM transition state is in some respects
intermediate between OA and SBM14 transition states (see
(8) (a) Chen, H.; Schlecht, S.; Semple, T. C.; Hartwig, J. F. Science 2000,
287, 1995. (b) Webster, C. E.; Fan, Y.; Hall, M. B.; Kunz, D.; Hartwig, J.
F. J. Am. Chem. Soc. 2003, 125, 858.
(9) (a) Periana, R. A.; Taube, D. J.; Gamble, S.; Taube, H.; Satoh, T.; Fujii,
H. Science 1998, 280, 560. (b) Periana, R. A.; Taube, D. J.; Evitt, E. R.;
Loffler, D. G.; Wentrcek, P. R.; Voss, G.; Masuda, T. Science 1993, 253,
340. (c) Shilov, A. E.; Shul'pin, G. B. Chem. Rev. 1997, 97, 2879. (d)
Lin, M.; Chen, S.; Garcia-Zayas, E. A.; Sen, A. J. Am. Chem. Soc. 2001,
123, 1000. (e) Jones, C. J.; Taube, D. J.; Ziatdinov, V. R.; Periana, R. A.;
Nielsen, R. J.; Oxgaard, J.; Goddard, W. A., III. Angew. Chem., Int. Ed.
2004, 43, 4626. (f) Xu, X.; Fu, G.; Goddard, W. A., III; Periana, R. A.
Stud. Surf Sci. Catal. 2004, 147, 499. (g) Stahl, S.; Labinger, J. A.; Bercaw,
J. E. Angew. Chem., Int. Ed. 1998, 37, 2181. (h) Shilov, A. E.; Shteinman,
A. A. Acc. Chem. Res. 1999, 32, 763. (i) Periana, R. A.; Ortmann, D. A.;
Dagmara, A.; Mironov, O. A. Presented at the 224th National Meeting of
the American Chemical Society, Boston, MA, August 18-22, 2002;
Abstract INOR-465. (j) Kua, J.; Xu, X.; Periana, R. A.; Goddard, W. A.,
III. Organometallics 2002, 21, 511. (k) Periana, R. A.; Ortmann, D. A.
Presented at the 223rd National Meeting of the American Chemical Society,
Orlando, FL, April 7-11, 2002; Abstract INOR-157.
(10) Vedernikov, A. N.; Caulton, K. G. Chem. Commun. 2004, 2, 162.
(11) (a) Jones, W. D. Acc. Chem. Res. 2003, 36, 140. (b) Jones, W. D.; Feher,
F. J. Acc. Chem. Res. 1989, 22, 91.
(12) Cundari, T. R. J. Am. Chem. Soc. 1994, 116, 340.
(13) Oxgaard, J.; Muller, R. P.; Goddard, W. A., III; Periana, R. A. J. Am.
Chem. Soc. 2004, 126, 352.
(14) (a) Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.; Nolan, M.
C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem. Soc.
1987, 109, 203. (b) Lam, W. H.; Jia, G.; Lin, Z.; Lau, C. P.; Eisenstein, O.
Chem. Eur. J. 2003, 9, 2775.
Scheme 2. Possible Routes for Catalytic C-H Functionalization
That Involve Net 1,2-Addition of C-H Bonds across M-X(R)
Bonds (X = O or NR)
Route A Route B
R-H' MXX Mn-R "X"
Mn-X H Mn-2
below) and is distinguished from the latter by more significant
interaction between the metal and the hydrogen of the carbon-
hydrogen bond being activated. The distinction between OA,
OHM, and SBM is reminiscent of many debates in chemical
bonding; while technical distinctions exist and demarcation into
categories can be useful, real mechanisms may lie on a spectrum
defined by these three classifications.
In addition to OA, SBM, and ES pathways for C-H
activation, the net 1,2-addition of C-H bonds across M-X (X
= heteroatomic ligand such as amido, alkoxo, imido, oxo, etc.)
bonds also holds promise as a step in overall catalytic C-H
functionalization.15 Only a few examples of net 1,2-addition of
C-H bonds across M-X bonds have been reported. For
example, the Wolczanski16 and Bergman'7 groups have studied
the 1,2-addition of C-H bonds, including that of methane for
the former group, across do metal-imido (M = NR) bonds of
early transition metals such as Ti and Zr. It has been established
that the reaction is an overall [20 + 2,] addition and that the
transition state has a four-centered arrangement preceded by
an alkane or arene adduct. The resulting alkyl/aryl product is
only a single C-N reductive elimination step away from
substrate functionalization to produce amine. However, reductive
elimination is difficult for electropositive early transition metal
complexes. In contrast, precedent for C-N and C-O reductive
elimination from late transition metals is extensive.18 Thus,
extension of the net 1,2-addition of C-H bonds to late transition
metal systems might ultimately be incorporated into catalytic
cycles for C-H functionalization.
(15) (a) Tenn, W. J., III; Young, K. J. H.; Bhalla, G.; Oxgaard, J.; Goddard, W.
A., III; Periana, R. A. J. Am. Chem. Soc. 2005, 127, 14172. (b) Feng, Y.;
Lail, M.; Barakat, K. A.; Cundari, T. R.; Gunnoe, T. B.; Petersen, J. L. J.
Am. Chem. Soc. 2005, 127, 14174. (c) Feng, Y.; Lail, M.; Foley, N. A.;
Gunnoe, T. B.; Barakat, K. A.; Cundari, T. R.; Petersen, J. L. J. Am. Chem.
Soc. 2006, 128, 7982.
(16) (a) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J. Am. Chem. Soc.
1988, 110, 8731. (b) Cummins, C. C.; Schaller, C. P.; Van Duyne, G. D.;
Wolczanski, P. T.; Chan, A. W. E.; Hoffmann, R. J. Am. Chem. Soc. 1991,
113, 2985. (c) Schaller, C. P.; Wolczanski, P. T. Inorg. Chem. 1993, 32,
131. (d) Bennett, J. L.; Wolczanski, P. T. J. Am. Chem. Soc. 1994, 116,
2179. (e) Schaller, C. P.; Bonanno, J. B.; Wolczanski, P. T. J. Am. Chem.
Soc. 1994, 116, 4133. (f) Schaller, C. P.; Cummins, C. C.; Wolczanski, P.
T. J. Am. Chem. Soc. 1996, 118, 591. (g) Bennett, J. L.; Wolczanski, P. T.
J. Am. Chem. Soc. 1997, 119, 10696. (h) Schafer, D. F., II; Wolczanski, P.
T. J. Am. Chem. Soc. 1998, 120, 4881. (i) Slaughter, L. M.; Wolczanski,
P. T.; Klinckman, T. R.; Cundari, T. R. J. Am. Chem. Soc. 2000, 122,
7953. (j) Cundari, T. R.; Klinckman, T. R.; Wolczanski, P. T. J. Am. Chem.
Soc. 2002, 124, 1481. (k) Cundari, T. R. J. Am. Chem. Soc. 1992, 114,
(17) (a) Hoyt, H. M.; Michael, F. E.; Bergman, R. G. J. Am. Chem. Soc. 2004,
126, 1018. (b) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
Soc. 1988, 110, 8729.
(18) The proclivity of late transition metals for C-O and C-N has been
profitably exploited in, for example, the well-known Hartwig-Buchwald
etheration and amination reactions. (a) Reductive: Stuermer, R. In Organic
Synthesis Highlights V; Schmalz,; H.-G., Wirth, T., Eds.; Wiley-VCH: New
York, 2003; p 22. (b) Muci, A. R.; Buchwald, S. L. Top. Curr. Chem.
2002, 219, 131. (c) Hartwig, J. F. In Comprehensive Coordination
Chemistry II: From Biology to Nanotechnology; McCleverty, J. A., Meyer,
T. J., Eds.; Elsevier: New York, Amsterdam, 2004; Vol. 9, p 369.
J. AM. CHEM. SOC. VOL. 129, NO. 43, 2007 13173
Key Step in Hydrocarbon Functionalization
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Cundari, Thomas R., 1964-; Grimes, Thomas V. & Gunnoe, T. Brent. Activation of Carbon-Hydrogen Bonds via 1,2-Addition across M-X (X = OH or NH2) Bonds of d6 Transition Metals as a Potential Key Step in Hydrocarbon Functionalization: A Computational Study, article, October 6, 2007; [Washington, DC]. (digital.library.unt.edu/ark:/67531/metadc77141/m1/2/: accessed November 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.