The transition-metal chemistry of amidinatosilylenes, -germylenes and -stannylenes

The transition-metal (TM) chemistry of heavier tetrylenes (HTs), also known as heavier carbene analogs, group 14 metalenes or group 14 metalylenes (compounds containing Si, Ge, Sn or Pb in +2 oxidation state), has experienced an exponential growth in the last few years because new families of HTs have emerged to the main-group chemistry arena. One of these families is characterized by the presence of an amidinato group attached to the group 14 element. Although the first report dealing with amidinato-HT-TM complexes appeared only seven years ago, nearly one hundred TM complexes containing amidinato-HT ligands are currently known and, remarkably, some of them have already been recognized as catalyst precursors for useful transformations of organic substrates (Sonogashira, Kumada and Negishi cross-couplings, ketone hydrosilylations, cycloadditions, arene C-H borylations, etc.). Thus, amidinato-HTs have emerged as promising alternatives to widely used classical ligands, such as phosphines or N-heterocyclic carbenes. This review comprehensively surveys the TM chemistry of amidinato-HTs published up to the end of 2014, examining not only the synthesis and characterization of these complexes, but paying special attention to reactivity studies, theoretical investigations and catalytic applications. (C) 2015 Elsevier B.V. All rights reserved.