A Cyclometalated N-Heterocyclic Carbene: The Wings of the First Pt2 (II,II) Butterfly Oxidized by CHI3.

The X-ray study on a single crystal of the butterfly-like complex [{Pt(C^C*)(μ-pz)}2 ] (1), containing a cyclometalated N-heterocyclic carbene ligand as wings (HC^C*=1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), showed three molecules in the asymmetric unit with intermetallic separations (Å) of 3.2294(4) (1A), 3.2834(4) (1B), and 3.1208(6) (1C). From the reaction of 1 with excess of CHI3 in the air and the sunlight, complex [{Pt(C^C*)(μ-pz)I)}2 ] (2) (dPt-Pt =2.6079(2) Å) was obtained as the major product, while [IPt(C^C*)(μ-pz)2 Pt(C^C*)CHI2 ] (3) (dPt-Pt =2.6324(3) Å) was obtained as the major product under argon atmosphere in the dark. Experimental and theoretical investigations showed that an easily accessible radical-like mechanism operates under thermal conditions, with dioxygen acting as an efficient radical (R. ) scavenger. The oxidation of a Pt2 (II,II) "butterfly" by CHI3 to give metal-metal bonded Pt2 (III,III) compounds is described now for the first time.