Structural and Spectroscopic Evidence of Strong Electronic Delocalization through a Cyanido Bridge in a Mixed‐Valence Os–Ru Complex

Abstract

We report the properties of a trinuclear cyanido-bridged complex, trans- [(dmap) 4 Ru II {(µ-NC)Os III (CN) 5 } 2 ] 4-[1 4-; dmap = 4-(dimethylamino)pyridine], whose structure and elecOver the last 40 years, considerable attention has been given to mixed-valence complexes, systems where an element presents more than one oxidation state, with transition metal compounds of group 8 as the more outstanding examples.[1] One of the areas of interest in this field is to identify systems in the frontier between the so-called localized systems or Class II, [2] according to the classification proposed by Robin and Day, [3] and the delocalized systems or Class III. To identify systems as Class III or Class II/ III (localized, but solvent-averaged) [4] several experimental criteria have been proposed [4,5] including (1) the shape, intensity and solvent dependence of the intervalence transition, (2) direct evidence of localization from crystal structure, spectroscopic markers, the appearance of symmetrical bridging-ligand vibrations and the appearance of nonaveraged spectator vibrations. Due to all the effort devoted to this area, several examples of Class III mixed-valence complexes have been identified, [6] and a few of them show identical coordination spheres for both centers in their crystal structures.[7] Non-symmetrical mixed-valence complexes have also been explored. The absence of symmetry could be due to the presence of a different ligand set for each metal atom, the presence of a non-symmetrical bridge or different elements with different redox states. In this case, a delocalized Class III system would not be symmetrical, and some of the previous experimental criteria can not be applied as they rely on the symmetry of the delocalized system. Cyanido-bridged dinuclear dimers are one of the most intensively studied families of mixed-valence complexes. [8] The exploration of the properties of these dimers, which are non-symmetrical due to the intrinsic asymmetric nature of the bridge, points to a strong coupling, measured through [a]

Influence of Central Metalloligand Geometry on Electronic Communication between Metals: Syntheses, Crystal Structures, MMCT Properties of Isomeric Cyanido‐Bridged Fe2Ru Complexes, and TDDFT Calculations

“…In the field of polynuclear cyanido‐bridged mixed valence complexes, the factors influencing electron‐transfer processes were subjected to a systematic study from the nature of the complexes to the environmental effects. The former is mainly based on the nature of the metals and their ligands, the orientation of the cyanido bridges and the shape and length of the chains,9 and the latter is mainly focused on solvent effects and salts effects 9h. 10 Much significantly, in this field, some trinuclear cyanido‐bridged mixed valence complexes have been constructed to simultaneously investigate long‐range electron‐transfer processes and the ability of the central metal to act as a bridge and to effect electronic communication 11.…”

Class III Delocalization in a Cyanide‐Bridged Trimetallic Mixed‐Valence Complex

“…A similar band has been reported for a related trimetallic system, trans-[Ru-(dmap) 4 {(m-NC)Os(CN) 5 } 2 ] 4À , the crystal structure of which also suggests a delocalized ground state. [21] (TD)DFT also provides an interpretation for the shoulder observed at ca. 7500 cm À1 .…”

“…[20,21] The complex [3](PF 6 ) 2 (Table 1) was prepared following the reported methods for the other trimetallic complexes, [18] but using trans-[Ru II (dmap) 4 (CN) 2 ] as the starting material; its identity was established by NMR spectroscopy (for experimental details, see the Supporting Information). Electrochemical exploration of this complex in acetonitrile reveals three reversible one-electron oxidations ( Figure 1).…”

Tris[4-(dimethylamino)pyridine][tris(pyrazol-1-yl)methane]ruthenium(II) bis(hexafluoridophosphate) diethyl ether monosolvate

“…For examples of other structures of ruthenium complexes of the Tpm ligand, see: Llobet et al (1989); Wilson & Nelson (2003); Katz et al (2005); Iengo et al (2005); Foxon et al (2007); Kuzu et al (2009); Waywell et al (2010); Zagermann et al (2011); De et al (2011); Agarwala et al (2011Agarwala et al ( , 2013; Serrano et al (2011); Cadranel et al (2012). For examples of other structures of ruthenium complexes of the dmap ligand, see: Bonnet et al (2003); Rossi et al (2008Rossi et al ( , 2010; Mutoh et al (2010); Dunbar et al (2011). For the closest related structure, see: Laurent et al (1999).…”

“…(2013). E69, m549-m550 been reported for the trinuclear complex in trans- [(dmap) Rossi et al, 2010). Considerably longer Ru-N(dmap) distances have been reported also, for example 2.333 (4) Å when positioned trans to a tellurocarbonyl ligand in trans,cis-Ru II Cl 2 (dmap) 2 (CTe)(H 2 IMes) (H 2 IMes = 1,3-dimesitylimidazolin-2-ylidene) (Mutoh et al, 2010), and as long as 2.338 (3) Å when located trans to a carbene ligand in trans,cis-Ru II Cl 2 (dmap) 2 (PCy 3 ) {CH(C 6 H 4 )-4-NMe 2 } (Dunbar et al, 2011).…”