Oxidative Route to Abnormal NHC Compounds from Singly Bonded [M–M] (M = Ru, Rh, Pd) Precursors

A new base-free entry to metal–aNHC compounds from metal–metal bonded bimetallic precursors and imidazolium salts is reported. Regioselective metalation proceeds via C–I oxidative addition of an annulated imidazo­[1,2-a]­[1,8]­naphthyridine system to [Ru^I–Ru^I], [Rh^II–Rh^II], and [Pd^I–Pd^I] single bonds, affording C⁵-bound (abnormal) Ru^II–, Rh^III–, and Pd^II–NHC compounds, respectively, at room temperature and in high yields.