Synthesis and exploratory coordination chemistry of the new ditertiary carbinamine ligand 2,6-bis(α-aminoisopropyl)pyridine

Abstract

The new pyridine-based N∩ N∩ N tridentate ligand 2,6-C 5H 3N(CMe 2NH 2) 2 ( 1) was synthesized by the treatment of 2,6-pyridinedicarbonitrile with an excess of the organocerium reagent in situ generated from CeCl 3 and methyllithium in THF. The reaction of 1 with [RuCl 2(PPh 3) 3] in THF at ambient conditions afforded ( OC-6-23)-[RuCl{2,6-C 5H 3N(CMe 2NH 2) 2}(PPh 3) 2]Cl ( 2). The corresponding dimethyl sulfoxide complex [RuCl{2,6-C 5H 3N(CMe 2NH 2) 2}{S(O)Me 2} 2]Cl ( 3) was isolated as a mixture of the ( OC-6-23) and ( OC-6-32) stereoisomers 3a and 3b from the reaction between 1 and ( OC-6-22)-[RuCl 2{S(O)Me 2} 3(OSMe 2)] in toluene at 80 °C. A prolonged interaction in toluene at reflux temperature gave isomerically pure 3a. The metal trichloride hydrates MCl 3 · xH 2O (M = Ru, Rh, Ir; x ≅ 2–4) produced mer-[RuCl 3{2,6-C 5H 3N(CMe 2NH 2) 2}] (M = Ru: 4; Rh: 5; Ir: 6), when combined with 1 in refluxing ethanol. The crystal structures of the following compounds were determined: ligand 1 and complexes 2– 5 as addition compounds 2 · CH 2 Cl 2, 3a · C 7 H 8, 4 · EtOH and 5 · 2 1 2 DMF .