Formation of CC and CC κ-Chelate Complexes through Competitive sp- and sp-CH Activations: An Experimental and Computational Study.

Depending on the chelate ring present, cyclometalated complexes are useful catalysts for various reactions. The reactivity of Ir and Rh NHC complexes bearing aliphatic or aromatic N,N'-substituents and thus featuring various metalation sites toward cyclometalation has been investigated. The Rh complex bearing an -mesityl-'-benzyl-NHC does not participate in any cyclometalation, while the Ir complex reacts under metalation of an -methyl group of the Mes substituent to give complex [] with a six-membered chelate ring. The Rh and Ir complexes bearing an --tolyl,-benzyl-NHC undergo sp-CH activation to yield the cyclometalated complexes [] and [] featuring a five-membered CC chelate ring. Density functional theory (DFT) studies corroborated the experimental findings.