No abstract

Geminal frustrated Lewis pairs (FLPs) are expected to exhibit increased reactivity when the donor and acceptor sites are perfectly aligned. This is shown for reactions of the nonfluorinated FLP tBu(2)PCH(2)BPh(2) with H(2), CO(2), and isocyanates and supported computationally.

Mn(i) PNP pincer hydride complexes were shown for the first time to catalyse the hydrogenation of CO2 to formate reaching quantitative yields and high TONs.

Fe­(II) hydrido carbonyl complexes supported by PNP pincer ligands based on the 2,6-diaminopyridine scaffold were found to promote the catalytic hydrogenation of CO2 and NaHCO3 to formate in protic solvents in the presence of bases, reaching quantitative yields and high TONs under mild reaction conditions, with pressures as low as 8.5 bar and temperatures as low as 25 °C. NMR and DFT studies highlighted the role of dihydrido and hydrido formate complexes in catalysis.

The linear tetraphosphine 1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (tetraphos-1, P4) was used as its rac and meso isomers for the synthesis of both molecularly defined and in situ formed Fe­(II) complexes. These were used as precatalysts for sodium bicarbonate hydrogenation to formate and formic acid dehydrogenation to hydrogen and carbon dioxide with moderate to good activities in comparison to those for literature systems based on Fe. Mechanistic details of the reaction pathways were obtained by NMR and HPNMR experiments, highlighting the role of the Fe­(II) monohydrido complex [FeH­(rac-P4)]+ as a key intermediate. X-ray crystal structures of different complexes bearing rac-P4 were also obtained and are described herein.