Contemporary developments in transition metal boryl complexes: An overview

Abstract

Transition metal (TM) complexes of boron comprising two-center two-electron (2c–2e) bond/s are systematically developed over the decades. Among them, TM boryl complexes (i.e. LnM–BR2) featuring tri-coordinated boron have been studied extensively because of their unique bonding pattern and diverse reactivity towards organic substrates. These TM boryl complexes were found to be the key intermediates in many catalytic cycles, for example, diboration, hydroboration and C–H borylation reactions. As a result, this field has drawn immense attention in the recent years to develop new molecules. Synthesis and structural characterization of various TM boryl complexes implicitly directed to the isolation of TM complexes containing hitherto unknown structural motif, which could not be isolated in pure main group chemistry. The present review gives a summary of the contemporary progresses for the synthesis and reactivity of various TM boryl complexes reported by others and us. This review offers a detailed discussion on the structure and bonding of the TM boryl complexes. In addition, some of the potential applications of these species in various organic transformations are discussed.