Ruthenium hydrogenation catalysts with P–N–N–P ligands derived from 1,3-diaminopropane and the formation of a β-diiminate complex by a base-induced isomerization

Abstract

The complexes RuHCl{PPh 2(2-C 6H 4)CH NCH 2CH 2CH 2N CH(2-C 6H 4)PPh 2} (RuHCl{prP 2N 2}, 7) and RuHCl{PPh 2(2-C 6H 4)CH 2NHCH 2CH 2CH 2NHCH 2(2-C 6H 4)PPh 2} (RuHCl{prP 2(NH) 2}, 8) are prepared by reaction of RuHCl(PPh 3) 3 with a ligand derived from 1,3-diaminopropane and ortho-diphenylphosphinobenzaldehyde. They are active precatalysts for the hydrogenation of acetophenone and are moderately active for the hydrogenation of benzonitrile and imines. The related complex RuHCl{ethP 2(NH) 2} with a ligand derived from 1,2-diaminoethane provides a more active catalyst. Complexes 7 and 8 undergo an unusual base-promoted isomerization reaction that produces a ruthenium complex containing a novel β-diiminato ligand.