Mixed‐Valence States Stabilized by Proton Transfer in a Hydrogen‐Bonded Biimidazolate Rhenium Dimer

Abstract

Di‐Re straits: Synchronized motion of protons and electrons, as shown in the scheme, has been observed in a hydrogen‐bonded Re dimer complex. The mixed‐valence states obtained by electrochemical redox reactions are stabilized by proton transfer within the dual hydrogen‐bonding site between 2,2′‐biimidazolate ligands.

fac-Acetato-bis(pyrazole) complexes: A systematic study on intra- and intermolecular hydrogen bonds

“…This is one of the big challenges of chemistry, that is, the understanding and control of the organization of molecules [4]. Hydrogen bonded organic aggregates have so far been object of main attention, but the presence of metals in supramolecular systems is attracting increasing interest, as they may show redox [5], optical [6], magnetic [7], adsorption [8], or catalytical [9] properties. We considered that complexes containing the fac-''MX(pz * H) 2 " (X = halogen, pz * H = any pyrazole) moiety [10] could be good precursors to start this study, if the halogen is replaced by another ligand able to establish hydrogen bonding interactions with the hydrogens of pyrazoles.…”

Mixed Valency in Quadruple Hydrogen-Bonded Dimers of Bis(biimidazolate)dirhodium Complexes

“…7 The dirhodium complexes are useful modules because they change the highest occupied molecular orbital (HOMO) with substitution of the equatorial and axial ligands. 7b For example, the π*-HOMO in [Rh 2 (O 2 CMe) 4 (H 2 O) 2 ] was altered to σ-HOMO when H 2 O was substituted by PPh 3 . There are some examples of halflantern-type complexes with two planar chelate ligands such as bipyridine and phenanthroline.…”

“…Biimidazole was provided by Prof. Tadokoro 4 ] (82 mg, 0.13 mmol) and H 2 bim (37 mg, 0.27 mmol) were placed in a flask, and 20 mL of dichloromethane was added. Reflux of the solution for 24 h under argon atmosphere afforded an olive-green suspension.…”

“…K c values for the oxidized and reduced species of [Re III Cl 2 (PBu 3 ) 2 (Hbim)] 2 are 5.41 × 10 4 and 1.14 × 10 4 , respectively, as calculated from the redox potentials 4. The values for the dimers of dimolybdenum complexes are 111−487 5.…”

Synthesis and structural characterization of the novel unusual oxido-bridged rhenium complex with Re atoms in two different coordination environments

“…In (2) the two Re centres are linked through a double oxido bridge and are crystallographically equivalent. A Re III,IV mixed-valence state has also been recorded for a hydrogen-bonded biimidazolate rhenium dimer as a result of an unprecedented stabilization by proton transfer [15]. An example of a polynuclear cluster compound with Re III and Re IV centres is tetra-n-butylammonium trans-octakis(μ 3 -sulfido)-tetrachloridodipyridylpentarhenium(III)rhenium(IV) [16].…”