Influence of gold nanoparticles applied to catalytic hydrogenation of acetophenone with cationic complexes containing ruthenium.

Abstract

Herein the catalytic activity of cationic ruthenium(II) complexes [Ru]+ is described in the presence of gold nanoparticles (AuNPsn ) in the transfer hydrogenation of acetophenone, to produce phenylethanol. The catalytic activity of the complexes, with a general formula cis-[RuCl(CH3OH)(P–P)(N–N)]+ or cis- [RuCl(CH3OH)(P)2(N–N)]+ {where: P ¼ triphenylphosphine (PPh3); P–P ¼ 1,1-bis(diphenylphosphino) methane (dppm); 1,2-bis(diphenylphosphino)ethane (dppe); 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb); N–N ¼ 2,20-bipyridine; 4,40-dimethyl-2,20-bipyridine} was investigated in the presence of AuNPsn . The interaction between [Ru]+ and AuNPsn citrate capped is an electrostatic interaction, by a self-assembly processes, to produce a supramolecular species, labeled as [Ru]+/AuNPsn . This non-covalent interaction has no effect over the chemical and physical chemical parameters of the complexes, which provides a good point of comparison in the presence and absence of AuNPsn . The AuNPsn alone have no catalytic activity in the transfer hydrogenation of acetophenone within 24 h of reaction. However, the AuNPsn have improved the catalytic activity of the complexes that have biphosphines with tensioned or large bite angle, while for the complexes that have biphosphines with a strong chelate effect a decrease in the catalytic activity was observed. The evidence is supported by experimental values of the yields of the hydrogenated product and DFT calculations of the “RuP–P” intermediates. Suitable crystals of cis-[RuCl2(dppe)(bipy)], cis-[RuCl2(dppp)(bipy)] and cis- [RuCl(CH3OH)(dppb)(bipy)](PF6) were obtained and the X-ray structures are presented here.