NMR: A good tool to ascertain σ-silane or σ-borane formulations?

NMR has played a major role in the characterization of dihydrogen complexes and a number of polyhydrides have been reformulated as dihydrogen complexes on the basis of NMR data. If dihydrogen complexes remain the most widely studied class of sigma-complexes, silane compounds are also well recognized as an important family of sigma-complexes and more recently a few sigma-borane compounds have been isolated. One important problem is the discrimination between a a-formulation and the corresponding hydrido(silyl) or hydrido(boryl) oxidative addition product. In this review we will discuss key literature data on silane and borane complexes to illustrate the benefit gained by using multinuclear NMR spectroscopy to better define the structures and bonding modes. Our goal is also to help the reader to appreciate the limits of the method and to provide valuable insights into the problem of secondary interactions. (C) 2008 Elsevier B.V. All rights reserved.