Iron/Lewis acid co-catalysts hydrogenate to CO2 to formate with unprecedented turnover for a first row transition metal catalyst.

The redox-active pincer ligand derived from bis(3,5-di-tert-butyl-2-phenol)amine, [ONO cat ]H 3 , enables reductive elimination of di-tert-butyldisulfide from a putative iron(III) dithiolate complex. The quinonate synthon of the ligand, [ONO q ]K, was used to prepare [ONO q ]FeX 2 complexes (1, X ¼ Cl; 2, X ¼ N(SiMe 3 ) 2 ), which were characterized by single-crystal X-ray diffraction, EPR and Mössbauer spectroscopies and identified to be high-spin iron(III) complexes. The protonolysis of 2 with tetrachlorocatechol afforded either monomeric [ONO q ]Fe(ortho-C 6 O 2 Cl 4 )(py) (3) or dimeric {[ONO q ] Fe(ortho-C 6 O 2 Cl 4 )} 2 (4). In contrast, the protonolysis of 2 with tert-butylthiol resulted in the extrusion of di-tert-butyldisulfide and the formation of a [ONO cat ]Fe fragment trapped with pyridine as monomeric [ONO cat ]Fe(py) 3 (5) or dimeric {[ONO cat ]Fe(py)} 2 (6). These results indicate that the [ONO]Fe platform can promote reductive elimination of disulfide without incurring changes to the metal oxidation state.

Synthetic and magnetic studies of homo- and heterobimetallic complexes of the redox-active ONO pincer ligand.