Infrared spectra of XCIrX3 and CX2IrX2 prepared by reactions of laser-ablated iridium atoms with halomethanes

Abstract

Small iridium high oxidation-state complexes with carbon–iridium multiple bonds are identified in the product matrix infrared spectra from reactions of laser-ablated Ir atoms with tetra-, tri- and dihalomethanes. In contrast to the previously studied Rh case, Ir carbyne complexes (XCIrX₃) are generated in reactions of tetrahalomethanes, and their short Ir–C bond lengths of 1.725–1.736 Å are appropriate for the carbon–metal triple bonds. DFT calculations also show that the Ir carbynes with an Ir–F bond have unusual square planar structures, similar to the recently discovered Ru planar complexes. Diminishing preference for the carbyne complexes leads to methylidene product absorptions in the tri- and dihalomethane spectra, marking a limit for generation of small metal carbynes. The insertion complexes, on the other hand, are not observed in this study, suggesting that X migration from C to Ir following initial C–X insertion is swift.