Agostic interactions in transition metal compounds

^aDepartment of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290,
^cInorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX13QR, United Kingdom; and
^dDepartment of Chemistry, Columbia University, New York, NY 10027

Edited by John E. Bercaw, California Institute of Technology, Pasadena, CA, and approved February 23, 2007 (received for review February 8, 2007)

Abstract

The impact of agostic interactions (i.e., 3-center–2-electron MHC bonds) on the structures and reactivity of organotransition metal compounds is reviewed.

Footnotes

^bTo whom correspondence may be addressed. E-mail: brookhar{at}email.unc.edu, malcolm.green{at}chemistry.ox.ac.uk, or parkin{at}columbia.edu
Author contributions: M.B., M.L.H.G., and G.P. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
↵ e For a review of α- and β-hydrogen elimination processes, see ref. 1.
↵ f Although there are two reports of complexes in which alkanes are in the vicinity of the metal center (refs. 20 and 21), there is no spectroscopic evidence that the alkane remains coordinated to the metal in solution. Furthermore, for one of these complexes (ref. 21), both the metal and alkane are disordered so that the precise details of the interaction are uncertain.
↵ g For recent examples of σ-complexes that have been characterized by NMR spectroscopy, see refs. 22–24.
↵ h For recent reviews, see refs. 25–27.
↵ i For a recent example, see ref. 28.
↵ j For other examples, see refs. 33–36.
↵ k Venanzi and coworkers (37) also offered another interpretation for “pregostic”: agostic of the weak type described by Pregosin.
↵ l MH–C interactions that are not agostic have also been referred to as pseudo-agostic (see ref. 39).
↵ m For a recent analysis of MH–C interactions in d⁸ Ni, Pd, and Pt compounds, see ref. 43.
↵ n For a recent review of theoretical aspects of agostic interactions, see ref. 47.
↵ o This view of the bonding in agostic compounds is necessarily simplistic. For a more detailed discussion, see ref. 48.