Electronic interactions in [Ru3(mu3-R² CCC6H4-4-R¹)(mu -dppm)(mu-CO) (CO)7] (R¹ = NO2 and R² = Fc; R¹ = NO2, CN and R² = Ph)

Abstract

A coordenação de FcCCC 6 H 4 -4-NO 2 (1) a uma carbonila polinucleada (cluster) de rutênio resultou na formação de [Ru 3 (µ 3 -FcCCC 6 H 4 -4-NO 2 )(µ-dppm)(µ-CO)(CO) 7 ] (2). Os voltamogramas cíclicos destes compostos e dos clusters análogos [Ru 3 (µ 3 -η 2 -C 6 H 5 CCC 6 H 4 -4-R)(µ-dppm)(µ-CO)(CO) 7 ] (R= H, 3; CN, 4; NO 2 , 5) permitiram avaliar as comunicações eletrônicas entre os diferentes sítios de oxi-redução (grupos ferrocenil e -NO 2 e o fragmento Ru 3 ) e analisar as capacidades relativas doadora-receptora de cada um dos três centros de oxi-redução que compõem 2. Além disto, a inércia de 2, em comparação com os clusters 3-5, os quais sofrem fácil perda de CO, foi atribuída à interação entre o grupo ferrocenil e a base metálica.The co-ordination of FcCCC 6 H 4 -4-NO 2 (1) to a ruthenium carbonyl cluster to yield [Ru 3 (µ 3 -FcCCC 6 H 4 -4-NO 2 )(µ-dppm)(µ-CO)(CO) 7 ] (2) is reported. The cyclic voltammograms of these compounds and of the analogous clusters [Ru 3 (µ 3 -η 2 -C 6 H 5 CCC 6 H 4 -4-R)(µ-dppm)(µ-CO)(CO) 7 ] (R= H, 3; CN, 4; NO 2 , 5) allowed an evaluation of the electronic communications between the different redox sites (ferrocenyl and -NO 2 groups, and Ru 3 moiety) and an analysis of the relative electron donor-acceptor capabilities of each of the three redox centres that compose 2. Furthermore, the inertness of 2, compared with clusters 3-5 which loose CO readily was attributed to the interaction between the ferrocenyl group and the metallic frame.Keywords: ruthenium cluster, ferrocene, alkyne, cyclic voltammetry IntroductionStudies of electronic interactions in systems containing multiple redox-active centres are of fundamental importance in the development of molecular-based electronic devices.1 Alkynes can be an elegant option in the search of systems containing multi-redox sites, once they can serve as conjugated bridges between groups of different electronic densities.2 In addition, they are remarkably versatile in their co-ordinating abilities to different metals (σ or π-fashion), that can result in the generation of novel mono or polynuclear metal complexes with attractive properties.3 Compounds derived from ferrocene have been extensively investigated for materials science 4 due to their low cost, stability and interesting redox properties, and can be used in molecular ferromagnets, molecular sensors, electrochemical agents, liquid crystals and non-linear optical materials. 5The aim of this work was to combine the electronic properties of alkynes, the ferrocenyl fragment and carbonyl clusters to build a new supramolecular compound containing various redox sites. Co-ordination of the ferrocenylalkyne FcCCC 6 H 4 -4-NO 2 (1) to a ruthenium carbonyl cluster to produce [Ru 3 (µ 3 -FcCCC 6 H 4 -4-NO 2 )(µ-dppm)(µ-CO)(CO) 7 ] (2) was therefore investigated. In cluster 2, the ferrocenyl fragment can act as an electron donor in charge-transfer processes, 6 the -NO 2 group as an electron acceptor 7 and the ruthenium moiety as a reservoir of electrons, depending on the co-ordinated ligands...