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

• Published in: Polyhedron Vol. 62; pp. 75 - 82
• Main Authors: Cavarzan, Deividi A., Fagundes, Francisco D., Fuganti, Otávio, da Silva, Caroline W.P., Pinheiro, Carlos Basílio, Back, Davi F., Barison, Andersson, Bogado, André L., de Araujo, Márcio P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 07.10.2013
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.06.022

Complexes with the general formula trans-[RuCl2(CO)(PR3)(N–N)] (N–N=diimines and/or amines; PR3=triphenylphosphine or tri-p-tolylphosphine) were synthesized by reacting trans-[RuCl2(CO)(dmf)(PR3)2] (dmf=N,N-dimethylformamide) and the appropriate N–N donor ligands and the complexes were tested 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 24h, whereas the proportion 1:20:500 furnished conversions up to 96% in 4h. The complexes containing the ligands ampy and en were the most active – the “RuH-NH” unit promoted reactions via the outer-sphere mechanism. We synthesized complexes with the general formula trans-[RuCl2(CO)(PR3)(N–N)] (N–N=diimines and/or amines; PR3=triphenylphosphine or tri-p-tolylphosphine) by reacting trans-[RuCl2(CO)(dmf)(PR3)2] (dmf=N,N-dimethylformamide) and the appropriate N–N donor ligands. We characterized the complexes by NMR (31P, 1H, nOe, HMBC, and HSQC), FTIR, and elemental analyses; we also analyzed trans-[RuCl2(CO)(PPh3)(bipy)], trans, trans-[RuCl2(CO)(P{p-tol3})(ampy)] and trans, trans-[RuCl2(CO)(PPh3)(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 24h, whereas the proportion 1:20:500 furnished conversions up to 96% in 4h. In addition, p-substituted acetophenone were reduced with conversions up to 95% within 135min 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.