Control in Advanced Biofuels Synthesis via Alcohol Upgrading: Catalyst Selectivity to n‐Butanol, sec‐Butanol or Isobutanol

Abstract Ruthenium complexes with tetradentate PNNP donor ligands demonstrate a marked change in selectivity compared to analogous bis bidentate PN complexes in Guerbet catalysis, producing mixtures of n ‐butanol (17 %), sec ‐butanol (14 %) and ethyl acetate (66 %) rather than the usual 90 %+ selectivity to n ‐butanol. Tridentate PNP ruthenium complexes such as [Ru(H)(Cl)(CO)(Ph 2 PCH 2 CH 2 NHCH 2 CH 2 PPh 2 )] also produce sec ‐butanol and, in optimized conditions (120 °C, 10 mol% NaOEt base), achieve 71 % selectivity to this butanol isomer. The same tri‐ and tetradentate complexes are efficient catalysts for the conversion of methanol/ethanol mixtures to isobutanol (up to 97 % selectivity). In this way, judicious choice of ligand within this general catalyst family allows selectivity to three butanol isomers of interest as fuel molecules.