Pseudotetrahedral organocobalt(III) compounds containing specific coordination sites for Bronsted acids

Transmetallation of the lithiated derivative 2,6-bis[dimethyl(amino)methyl] phenyllithium with the cobalt(III) centre of the dimer bis[(eta(5)-cyclopen tadienyl)cobalt(iodo)(mu-iodo)] has been found to afford the organocobalt c ompound [CoI{2-(Me2NCH2)-6-(Me2NH+CH2)C6H3}(eta(5)-C5H5)]I 3, in which the potentially terdentate (pincer) ligand is bound to Co through the formerly lithiated aryl carbon atom and one NMe2 unit only, whilst the second NMe2 g roup is protonated by HI. In the presence of aqueous KPF6, 3 has been found to undergo both substitution of the iodide bound to Co by a water molecule and deprotonation of the Me2NH group to afford [CoI{2,6-(Me2NCH2)(2)C6H3}( eta(5)-C5H5) (H2O)]PF6, 4a It was found that the water ligand in 4a could b e substituted by neutral ligands such as PMe2Ph as well as by Bronsted acid s such as HCl, HI, HF, or HOAc to afford the compounds [CoX{2-(Me2NCH2)-6-( Me2NH+CH2)C6H3}(eta(5)-C5H5)]PF6, 5a-d, where X = Cl, I, F, or OAc, respect ively. Crystal structure analyses of some representative examples of these compounds, including 4a, have shown unambiguously that an intramolecular hy drogen bond is present between X and the proton of the Me2NH+ unit. H-1-NMR evidence that this interaction persists in solution has been found for com pounds 4a, 5a, 5c, and 5d.