Thermally Stable Monoruthenium Acetylide Radical Species

Abstract

Control of radical reactivity is regarded as an important concern in the fields of catalysis and materials sciences. Radical species generated from monoruthenium acetylide complexes are, in general, highly reactive, and therefore structural characterization of these species has remained elusive. In this paper, a spectroscopic and structural characterization of the cationic radical species of a monoruthenium diacetylide bearing a Ru tetraphosphine fragment, [trans-(Ar–SC≡C)2Ru(dppe)2]SbCl6 ([1]+SbCl6) [Ar: p-t-BuC6H4; dppe: 1,2-bis(diphenylphosphino)ethane], is presented. The formation of the radical species [1]+ is supported by the vis-NIR, IR, and ESR studies. Furthermore, the solid-state structure of [1]+ reveals a significant contribution of the cumulenic Ru=C=C=S resonance structure. Remarkably, the thermal stability of [1]+ results from the incorporation of the electron-donating (arylsulfanyl)ethynyl ligands and the highly sterically demanding dppe ligands as compared with a monoruthenium complex with less-bulky and less-electron-rich derivatives.

Controlling Redox and Wirelike Charge-Delocalization Properties of Dinuclear Mixed-Valence Complexes with MCp*(dppe) (M = Fe, Ru) Termini Bridged by Metalloporphyrin Linkers

“…wirelike behavior, can be effectively controlled by appropriate design of the BL, such as substituents, − π-extension, − metal complexation, , and various external stimuli. − However, the interactions between the two metal centers usually deteriorate exponentially upon extension of the BL . In this context, polyyne-diyl complexes ML n -(CC) m -ML n have been expected to show long-range electronic interaction between the terminal metal fragments due to the interactions of the two perpendicularly oriented π-systems of the polyynediyl bridge with the metal d orbitals. − The corresponding 1e-oxidized MV complexes, however, are thermally unstable due to the high radical reactivity of the carbon chains , and, thus, their propensity to support long-range electron transfer has remained unclear (Figure b) . Stability of the MV complexes can be improved by introduction of phenylene rings ML n -CC-( p -C 6 H 4 ) m -CC-ML n , but their wirelike performance is not always good because one of the dπ-pπ interactions was interfered by the inserted sp 2 -hybridized phenyl rings.…”