EFFECT OF SECOND-SPHERE COORDINATION .6. ADDUCT FORMATION OF MONOAMMINE-RUTHENIUM(II), DIAMMINE-RUTHENIUM(II), TRIAMMINE-RUTHENIUM(II) AND TETRAAMMINERUTHENIUM(II) COMPLEXES WITH 18-CROWN-6 ETHER

Adduct formation was spectrophotometrically and electrochemically inve stigated for monoammine-, diammine-, triammine- and tetraamminerutheni um(II) complexes. It was found that an adduct was formed through hydro gen bonding between the coordinating ammonia ligands to the ruthenium( II) and the ether oxygens of 18-crown-6 ether. The stoichiometry of ad duct formation was determined to be a 1:1 ratio of complex to 18-crown -6 ether. The electrochemical results offer the evidence that the incr eased electron density around the metal center by formation of the hyd rogen bond is redistributed over the whole complex through p pi-d pi b ack donation. The electrochemical behavior in the presence of 18-crown -6 ether revealed the concurrent electrode reactions for the ruthenium (II)-ammine complexes with fewer ammine ligands.