Pincer complexes, leading characters in C-H bond activation processes. Synthesis and catalytic applications

The direct functionalization of C-H bonds is in many ways a simple and desired reaction. This strategy could decrease the amount of wastes and energy in a given process. Thus, it is attractive from an environmental and economical point of view. However, C-H bonds are usually strong and kinetically inert; hence, their activation remains a challenging transformation. In addition, the control of the selectivity in C-H activation is difficult to achieve, and the use of 'directing' groups is often necessary. Moreover, homogeneous catalysis mediated by transition metals is one of the most effective strategies to achieve good selectivity and control of C-H activation. Pincer complexes have been employed as efficient catalysts for C-H activation, allowing the functionalization of alkanes, arenes, allyl cyanides, among others. Thus, for the las two decades, pincer complexes have stand out as useful tools in catalysis, due to their well-known high thermal stability and increased activity, as well as their facile synthesis and functionalization. Hence, the present paper summarizes some of the most relevant advances in C-H activation using pincer compounds. In which we have focused both on the synthesis of pincer complexes via C-H activation and reactions catalysed by pincer complexes involving C-H activation processes. (C) 2019 Elsevier B.V. All rights reserved.