Hydroxypyridine/Pyridone Interconversions within Ruthenium Complexes and Their Application in the Catalytic Hydrogenation of CO 2

• Published in: Inorganic chemistry 2023-05, Vol.62 (17), p.6704-6710
• Main Authors: Ayyappan, Ramaraj, Das, Uttam Kumar, Abdalghani, Issam, Da Costa, Rosenildo C, Tizzard, Graham J, Coles, Simon J, Owen, Gareth R
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c00287

Reaction of a new ligand (6-diisopropylphosphino-2-pyridone) with 0.5 equiv of [RuCl ( -cymene)] resulted in the formation of a mixture of [RuCl ( -cymene)(κ - )] ( ) and [RuCl( -cymene)(κ - - )]Cl ([ ] ) (where = 6-diisopropylphosphino-2-hydroxypyridine). The ratio between the two products can be controlled by the nature of the solvent. The similar reaction between and [RuCl ( -cymene)] in the presence of AgOTf and Na[BArF ] (where BArF = [{3,5-(CF ) C H } B] ) resulted in the formation of the complexes [RuCl( -cymene)(κ - - )]OTf, ([ ] ) and [RuCl( -cymene)(κ - - )]BArF ([ ] ), respectively. Reactions between complex [ ] , [ ] , or [ ] and a base (either DBU or NaOMe) resulted in the deprotonation of the hydroxyl functional group to form a novel neutral orange-colored dearomatized complex, . The identity of complex was confirmed as [RuCl( -cymene)(κ - - )], where is the anionic species (6-diisopropylphosphino-2-oxo-pyridinide), which contains the deprotonated moiety. The new ligand and its corresponding air stable half-sandwich derivative ruthenium complexes , [ ] , [ ] , and were all isolated in good yields and fully characterized by spectroscopic and analytical methods. The interconversions between the neutral and anionic forms of the ligands , , and offer the potential for novel secondary sphere interactions and proton shuttling reactivity. The consequences for this have been explored in the activation of H and the subsequent catalytic hydrogenations of CO into formate salts in the presence of a base.