The Synthesis and Properties of an Encapsulated Ruthenium(II) Ion by an N3S3 Macrobicyclic Ligand

Abstract

The complex [ Ru(capten)]2+ ( capten = 1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]- icosane ) has been synthesized from [ Ru ( dmf )6]2+ ( dmf = N,N- dimethylformamide ) and the free ligand . An X-ray crystallographic analysis of [ Ru ( capten )] (CF3SO3)2 at 138 K reveals a lel3 conformation of the ligand with an average II-N bond length of 2.136(5) � and an average RuII-S bond length of 2.284(8) � . Visible spectra and the redox potential (1.26 V v. n.h.e .) show that the RuII state is stabilized by c. 0.9 V relative to the complex with six nitrogen donor atoms. Oxidation of Ru11 to RuIIIin acetonitrile leads to dehydrogenation of the ligand to form an imine. Successive oxidations lead to a triimine species where all the imines are located in the ligand cap. These oxidation processes are inferred to take place through RuIV intermediates which decay by intramolecular 2e- steps to the imine.