Heterolytic σ ‐Bond Activation by Transition Metal Complexes

Abstract

Introduction s-Bond activation by transition metal complexes is of considerable importance in modern organometallic and catalytic chemistry and remains a challenging research target. For instance, the CaH s-bond activations of alkane and aromatics are the first step in introducing the functional group into alkane and aromatic compounds [1], respectively. Theoretical studies of the s-bond activation are extremely desirable and allow elucidation of the roles of numerous factors (both electronic and steric in origin) in CaH, CaC, etc. bond functionalization.In general, there are three categories of s-bond activation reactions: (a) oxidative addition (Reaction 1), (b) metathesis (Reaction 2), and (c) s-bond addition across to the MbNR bond (Reaction 3).Oxidative addition is often observed in the late transition metal complexes and has been extensively investigated using theoretical approaches [2, 3]. Metathesis is observed for the both early and late transition metal complexes. Notably, when X is an anion in Reaction (2) the oxidation state of M does not change in metathesis and the s-bond activation occurs heterolytically. s-Bond addition to MbN bond is observed in both early and middle transition metal complexes. This reaction (Reaction 3) is considered to take place in a heterolytic manner, because N is electronegative and M is electropositive.Here, we present several examples of s-bond activation reactions. First, we mention the heterolytic s-bond activation reaction reported by Fujiwara and Moritani [4], where a CaH bond of benzene is activated by Pd (OAc) 2 and stylene is produced. Similar metathesis-like heterolytic s-bond activation has been 265