Rhenium Complexes Bearing Tridentate and Bidentate Phosphinoamine Ligands in the Production of Biofuel Alcohols via the Guerbet Reaction

We report a variety of rhenium complexes supported by bidentate and tridentate phosphinoamine ligands their use in the formation advanced biofuel isobutanol from methanol ethanol. Rhenium pincer 1–3 are effective catalysts for this process, with 2 giving 35% yields, 97% selectivity liquid fraction, over 16 h catalyst loadings as low 0.07 mol %. However, these show poorer overall selectivity, significant amount carboxylate salt solid byproduct also being observed. Production active 1d has been followed 31P NMR spectroscopy, importance presence base elevated temperatures to activation established. Complexes diphosphine inactive Guerbet chemistry; however, greater salts. The novel complex 7 was able produce 28% yield 17 h. N–H moiety catalytic performance established, further weight hypothesis that operate via cooperative mechanism.