Heterobi-, tri- and tetra-metallic cyanide-bridged complexes based on pentacarbonylcyanochromate(0) and penta-, cis-tetra- and fac-tri-ammineruthenium(III) groups: optical metal-metal charge transfer and electrochemical characteristics
摘要:
The heterobi-, tri- and tetra-metallic Robin-Day Class II mixed-valence complexes, [(OC)(5)Cr(mu-CN)Ru(NH3)(5)](2+) (CrRu), cis-[{(OC)(5)Cr(mu-CN)}Ru-2(NH3)(4)](+) (Cr2Ru) and fac-[{(OC)(5)Cr(mu-CN)}Ru-3(NH3)(3)] (Cr3Ru) have been synthesised directly by coupling [Cr(CO)(5)CN](-) with an appropriate penta-, tetra- or tri-ammineruthenium precursor and characterised by electrochemical, analytical and spectroscopic methods. The complexes exhibit solvent-ammine hydrogen-bonding induced solvatochromism in the MMCT energy which linearly varies with the Gutmann solvent donor number (DN) at 219, 158 and 116(+/-7) cm(-1)/DN respectively which corresponds to a linear variation of 51(+/-6) cm(-1)/DN/NH3 group. Electrochemical and spectroscopic evidence points to the ligating equivalence of [Cr(CO)(5)CN](-) and NH3 groups in this series. Cyclic and square-wave voltammograms, CV and SWV, show reversible couples at +0.45 and -0.36 V (versus ferrocene) for the chromium(0/I) and ruthenium(III/II) potentials in the complex set. Dispersion in CV and peak broadening in SWV, for CrxRu (x = 2, 3), indicate weak Cr-Cr coupling through the ammineruthenium centre corresponding to a separation of similar to 65 mV. We report electrochemical data for [(OC)(5)Cr(mu-CN)Os(NH3)(5)](2+) (CrOs) and its visibly spectacular solvatochromism (188 cm(-1)/DN) from blue to purple, red, orange and yellow colourations.