869477-40-7Relevant academic research and scientific papers
Heterosite effects in novel heteronuclear clusters [Os 2Ru(CO)11(PPh3)] and [Os2Ru(CO) 10(2-acetylpyridine-N-isopropylimine)]
Vergeer, Frank W.,Lutz, Martin,Spek, Anthony L.,Calhorda, Maria J.,Stufkens, Derk J.,Hartl, Frantisek
, p. 2206 - 2222 (2005)
A new synthetic route towards the mixed-metal cluster [Os 2Ru(CO)12] is described together with the syntheses of its PPh3 and iPr-AcPy (iPr-AcPy = 2-acetylpyridine-N-isopropylimine) derivatives. The molecular structures of the novel clusters [Os 2Ru(CO)11(PPh3)] and [Os2Ru(CO) 10(iPr-AcPy)] were determined on the basis of crystalline solid solutions of the Os2Ru and corresponding Os3 species. The structures reveal that coordination of the Lewis bases occurs exclusively at the ruthenium site of [Os2Ru(CO)12], which is in agreement with density functional theory (DFT) calculations on several structural isomers of these compounds. According to the time-dependent DFT results, the lowest optically accessible excited state of [Os 2Ru(CO)10(iPr-AcPy)] has a prevailing σ(Ru-Os2)-π*(iPr-AcPy) character, with a partial σσ* (Ru-Os2) contribution. In weakly coordinating 2-chlorobutane, the excited state has a lifetime τ = 10.4 ± 1.2 ps and produces biradicals considerably faster than observed for [Os 3(CO)10(iPr-AcPy) (τ = 25.3 ± 0.7 ps). In coordinating acetonitrile, the excited state of [Os2Ru(CO) 10(iPr-AcPy)] decays mono-exponentially with a lifetime τ = 2.1 ± 0.2 ps. In contrast to [Os3(CO)10(iPr-AcPy)] that forms biradicals as the main primary photoproduct even in strongly coordinating solvents, zwitterion formation from the solvated lowest excited state is observed for the heterometallic cluster. This is concluded from time-resolved absorption studies in the microsecond time domain. Due to the lower tendency of the coordinatively unsaturated +Ru(CO) 2-(iPr-AcPy-/0) moiety to bind a Lewis base, the heteronuclear biradical and zwitterionic photoproducts live significantly shorter than their triosmium counterparts. The influence of the weaker Os2-Ru(iPr-AcPy) bond on the redox reactivity is clearly reflected in very reactive radical anions formed upon electrochemical reduction of [Os 2Ru(CO)10(iPr-AcPy)]. The dimer [-Os(CO) 4-Os(CO)4-Ru(CO)2(iPr-AcPy)]2 2- is the only IR-detectable intermediate reduction product. The dinuclear complex [Os2(CO)8]2- and insoluble [Ru(CO)2(iPr-AcPy)]n are the ultimate reduction products, proving fragmentation of the Os2Ru core. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
