Mixed phosphine/diimines and/or amines ruthenium carbonyl complexes: Synthesis, characterization and transfer-hydrogenation

摘要

We synthesized complexes with the general formula trans-[RuCl _2(CO)(PR_3)(N-N)] (N-N = diimines and/or amines; PR _3 = triphenylphosphine or tri-p-tolylphosphine) by reacting trans-[RuCl_2(CO)(dmf)(PR_3)_2] (dmf=N, N-dimethylformamide) and the appropriate N-N donor ligands. We characterized the complexes by NMR (~(31)P, ~1H, nOe, HMBC, and HSQC), FTIR, and elemental analyses; we also analyzed trans-[RuCl_2(CO)(PPh _3)(bipy)], trans, trans-[RuCl_2(CO)(P{p-tol _3})(ampy)] and trans, trans-[RuCl_2(CO) (PPh _3)(ampy)] by X-ray diffraction. We tested the complexes as pre-catalyst for the reduction of acetophenone in transfer-hydrogenation conditions, using isopropanol as the hydrogen source. The catalyst/base/ substrate molar proportion of 1:20:1000 yielded conversions up to 83% in 24 h, whereas the proportion 1:20:500 furnished conversions up to 96% in 4 h. In addition, p-substituted acetophenone were reduced with conversions up to 95% within 135 min of reaction time. The complexes containing the ligands ampy and en were the most active-the "RuH-NH" unit promoted reactions via the outer-sphere mechanism.