Nickel complexes for catalytic C-H bond functionalization

The direct catalytic functionalization of traditionally unreactive C-H bonds is an atom-economic transformation that has become increasingly important and commonplace in synthetic applications. In general, 2 nd and 3 rd row transition metal complexes are used as catalysts in these reactions, whereas the less costly and more abundant 1 st row metal complexes have limited utility. This Perspective article summarizes progress from our laboratory towards understanding the fundamental issues that complicate the use of Ni complexes for catalytic C-H bond functionalization, as well as approaches to overcoming these limitations. In practice it is found that Ni complexes can functionalize C-H bonds by processes that, to date, have not been observed with the heavier metals. An example is provided by the catalytic stannylation of C-H bonds with tributylvinyltin, Bu 3 SnCH&z.dbd;CH 2 , which produces ethylene as a by-product. A search for fundamental understanding of how Ni complexes can be designed to undergo challenging C-H activation reactions provides an entry into unprecedented C-H functionalization reactions.