THE SYNTHESIS AND PROPERTIES OF AN ENCAPSULATED RUTHENIUM(II) ION BY AN N3S3 MACROBICYCLIC LIGAND

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 R(II)-N bond length of 2.136(5) angstrom and an average Ru(II)-S bond length of 2.284(8) angstrom. Visible spectra and the redox potential (1.26 V v. n.h.e.) show that the Ru(II) state is stabilized by c. 0.9 V relative to the complex with six nitrogen donor atoms. Oxidation of Ru(II) to Ru(III) in 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 Ru(IV) intermediates which decay by intramolecular 2e- steps to the imine.