Ambi-Valence Taken Literally: Ruthenium vs Iron Oxidation in (1,1′-Diphosphinoferrocene)ruthenium(II) Hydride and Chloride Complexes as Deduced from Spectroelectrochemistry of the Heterodimetallic “Mixed-Valent” Intermediates

Abstract

Combining two different redox-active organometallic moieties, we prepared the compounds [(Cym)RuCl(dpf)](PF6), with Cym = p-cymene = 1-isopropyl-4-methylbenzene, and the diphosphinoferrocenes (dpf) 1,1′-bis(diphenylphosphino)ferrocene (dppf; complex 3), 1,1′-bis(diisopropylphosphino)ferrocene (dippf; complex 4), and 1,1′-bis(diethylphosphino)ferrocene (depf; complex 5) as well as the structurally characterized hydride complex [(C5Me5)RuH(dippf)] (2). In contrast to the case for 2, with an approximately staggered ferrocene conformation, the chloride complexes 3−5 exhibit a syn-periplanar ferrocene arrangement due to a Cl···H(C5H4) interaction in the solid and in solution. The related new compounds [(Cym)RuH(dppf)](PF6) (6) and trinuclear (μ-dpf)[(Cym)RuCl2)]2 (7−9) were also obtained and identified by 1H and 31P NMR spectroscopy. The redox behavior of 2−6 and of the known [(C5Me5)RuH(dppf)] (1) was investigated using cyclic voltammetry, spectroelectrochemistry in the UV/vis/near-IR and IR regions, and, in part, by EPR. The first oxidation of the areneruthenium compounds 3−6 occurs reversibly at the ferrocene site, while the reduction proceeds via an ECE two-electron pattern under chloride dissociation. These results are compared to those obtained for the pentamethylcyclopentadienide/hydride complexes 1 and 2, which demonstrate unambiguously the ruthenium center as the site of the first electron loss. The different results for the two kinds of heterodimetallic d5/d6 mixed-valent intermediates, FeIIRuIII for 1 + and 2 + and FeIIIRuII for 3 + −6 + , are discussed with respect to the possible uses of such heterodinuclear systems in H2 conversion catalysis.

Synthesis and Characterization of Cerium and Yttrium Alkoxide Complexes Supported by Ferrocene-Based Chelating Ligands

“…5,[8][9][10][11][12][13][14] Metallocene-based chelating ligands offer the possibility to engage a redox-active metal center in strong electronic communication, raising the possibility of redox isomerism. [15][16][17] To test if such a situation occurs between ferrocene and a lanthanide, cerium, we focused on Schiff bases incorporating ferrocene. 1,1 0 -Di(2,4-bis-tert-butyl-salicylimino)ferrocene (1-H 2 , Chart 1) has already been used to generate various metal complexes; the Arnold group synthesized and characterized magnesium, titanium, and zirconium complexes, 18 while our group reported yttrium and cerium(IV) complexes.…”

Ruthenium Halide Complexes as N‐Alkylation Catalysts

“…From the same reaction of 1a and dppf in a 1:2 or 1:1 stoichiometric ratio, when performed in a non protic solvent such as dichloromethane or chloroform, we have isolated dimer 4c with the formula [(RuCl 2 ( p ‐cymene)) 2 (dppf)] (Figure 7). This compound has previously been prepared20b,20d,21 but, to the best of our knowledge, neither its catalytic behaviour or crystal structure have been reported. The structure of complex 4c was determined by X‐ray crystallography.…”

Synthesis, electrochemistry and IR spectroelectrochemistry of bisferrocenyl bridged benzene derivates

“…What is more, bridged biferrocenyl complexes have been focused on which two ferrocenyl units are connected by different covalent groups, so they can easily form mixed-valent (MV) Fe(Ⅱ)e Fe(Ⅲ) species by electrochemical or chemical oxidation [4,7,8]. Multi-ferrocenyl compounds, including multi-metallic mixedvalence, have received considerable attentions because of the ideal redox properties of the ferrocenyl group due to their applicabilities in molecular electronics, sensor applications and multi-redox catalysis [9,10]. In particular, they have been used extensively for electrochemical studies of the electronic intramolecular communications among covalently linked redox units.…”