Reactions of a quintuply bonded chromium dimer with alkynes

Abstract

Quintuply bonded [(H)L(iPr)Cr](2) reacts with alkynes RC≡CR (R = Me, Et, Ph, CF(3)) to form exclusively 1 : 1 adducts [(H)L(iPr)Cr](2)(RCCR). All products feature relatively short Cr-Cr distances (1.919-1.962 Å) and elongated C-C bonds (1.315-1.436 Å), consistent with [2+2] cycloaddition reactions. The hydrocarbon adducts are 4-membered metallacycles, the bridging alkynes of which are progressively skewed with respect to the Cr-Cr axis. In contrast, perfluoroalkyne adds across the metal ligand moiety.