Ethylene Coordination and Acetylene Dimerization at Tp′Ir^III Centers

The compound TpMs′′Ir(N2) (1·N2; TpMs′′ = doubly metalated hydrotris(3-mesitylpyrazol-1-yl)borate ligand) reacts with ethylene with formation of the adduct TpMs′′Ir(C2H4) (2), while with acetylene it gives TpMs′′Ir(H2CCHCCH) (3; the enyne coordinated through the CC double bond), as the result of the dimerization of the alkyne. Experimental and theoretical studies have been carried out in order to address the kinetic reactivity of the fragment [TpMs′′Ir] (1) toward C2H4 and C2H2 and the thermodynamic stabilities of the resulting adducts.