Addition of O-H, N-H, and F-H Bonds across a Boryl-Iridium Unit

(PBP)Ir(CO)(2) possesses a Lewis acidic boryl center and a basic monovalent Ir center. Heterolytic cleavage of O-H, N-H, and F-H bonds by this molecule was examined. (PBP)Ir(CO)(2) reacted with water, methanol, ethanol, cyclohexanol, phenols, benzoic acid, and triethylamine trihydrofluoride to add the O-H and F-H units across the B-Ir bond with preservation of both carbonyl ligands. For the benzoate adduct, one of the CO ligands is lost upon thermolysis with the benzoate bridging B and Ir. Thermolysis of (PBP)Ir(CO)(2) with (BuNH2)-Bu-n ultimately resulted in a monocarbonyl product of the N-H cleavage with the resultant amido group bridging B and Ir. Dicarbonyl intermediates were observed in this reaction. Structures of the X-H cleavage products and the possible mechanistic pathways are discussed. Mechanistic experiments indicate that the reaction with ROH substrates proceeds by initial protonation of Ir, consistent with slower reactions with less acidic ROH substrates (and no reaction with (BuOH)-Bu-t). For amines, the reaction appears to require coordination of the basic nitrogen to boron and to be limited by the basicity of the N and the steric encumbrance, as evidenced by lack of reaction of (PBP)Ir(CO)(2) with tert-butylamine, diethylamine, aniline, p-anisidine, and pyrrole.