Trans/cis isomerization of [RuCl2(diphosphine)(diamine)] complexes: Synthesis, X-ray structure and catalytic activity in hydrogenation

The diamine (NN) co-ligand 2,2-dimethyl-1,3-propanediamine and 2,3-diaminophathalene react individually with [RuCl2(dppb)2(μ-dppb)] to afford complexes with kinetically stable trans-[Cl2Ru(dppb)(NN)] as the favoured isomer. The thermodynamically stable cis-[Cl2Ru(dppb)(NN)] isomer of complex 1 was formed from the trans-1 isomer. The trans to cis isomerization reaction was conducted in CHCl3 at RT and monitored by 31P{1H} NMR. The structures of the desired complexes were characterized via elemental analyses, IR and, UV–visible spectroscopy, FAB-MS and NMR. The structure of the cis-1 isomer was determined by single crystal X-ray measurements. Both the trans-1 and cis-1 isomers were shown to have a significant catalytic role in selective hydrogenation reactions under mild conditions using cinnamic aldehyde as typical model reaction.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two new ruthenium(II) complexes of type trans-[RuCl2(dppb)(NN)] were made available. ► Trans to cis isomerization reaction of complex 1 was monitored by 31P{1H} NMR. ► The thermodynamically favored cis-1 isomer of complex 1 was confirmed by XRD crystal measurements. ► Synthesized complexes have showed very good catalytic activity in the hydrogenation of cinnamic aldehyde.