Verification of the Formation of Intramolecular-Coordination Bonds in Cyclometalation Reactions with Transition Metal Compounds

Abstract

Cyclometalation reactions have been carried out with most transition metal compounds. The first article on these reactions is generally thought to be a 1963 article on the reaction of an azobenzene with a nickel compound. However, the verification of the intramolecular bond was incorrectly assigned in that article as the N=N π-coordination bond to the nickel atom. For this reason, an article on the reaction of azobenzene with a Pd or Pt atom published in 1965 did not include verification of the coordination of nitrogen lone electron pair with a Pd or Pt atom, although the chemical equations were shown. Consequently, the verification of intramolecular-coordination bonds of azobenzene with the transition metals was delayed until 1969, which was later than the abovementioned report on our research on main group metal compounds in 1966.