title: Ruthenium complexes of C,C'-bis(ethynyl)carboranes: an investigation of electronic interactions mediated by spherical pseudo-aromatic spacers.
abstract: The complexes [Ru(1-C[triple bond]C-1,10-C2B8H9)(dppe)Cp*] (3a), [Ru(1-C[triple bond]C-1,12-C2B10H11)(dppe)Cp*] (3b), [{Ru(dppe)Cp*}2{mu-1,10-(C[triple bond]C)2-1,10-C2B8H8}] (4a) and [{Ru(dppe)Cp*}2{mu-1,12-(C[triple bond]C)2-1,12-C2B10H10}] (4b), which form a representative series of mono- and bimetallic acetylide complexes featuring 10- and 12-vertex carboranes embedded within the diethynyl bridging ligand, have been prepared and structurally characterized. In addition, these compounds have been examined spectroscopically (UV-vis-NIR, IR) in all accessible redox states. The significant separation of the two, one-electron anodic waves observed in the cyclic voltammograms of the bimetallic complexes 4a and 4b is largely independent of the nature of the electrolyte and is attributed to stabilization of the intermediate redox products [4a]+ and [4b]+ through interactions between the metal centers across a distance of ca. 12.5 A. The mono-oxidized bimetallic complexes [4a]+ and [4b]+ exhibit spectroscopic properties consistent with a description of these species in terms of valence-localized (class II) mixed-valence compounds, including a unique low-energy electronic absorption band, attributed to an IVCT-type transition that tails into the IR region. DFT calculations with model systems [4a-H]+ and [4b-H]+ featuring simplified ligand sets reproduce the observed spectroscopic data and localized electronic structures for the mixed-valence cations [4a]+ and [4b]+.
authors.affiliation: Department of Chemistry, Durham University, South Rd, Durham, DH1 3LE, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fox
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Roberts
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Baines
authors.forename: Boris Le
authors.initials: BL
authors.lastname: Guennic
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Halet
authors.forename: Frantisek
authors.initials: F
authors.lastname: Hartl
authors.forename: Dmitri S
authors.initials: DS
authors.lastname: Yufit
authors.forename: David
authors.initials: D
authors.lastname: Albesa-Jové
authors.forename: Judith A K
authors.initials: JA
authors.lastname: Howard
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Low
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004583:Electrons; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods
chemical_list: D001896:Boron Compounds; D008024:Ligands; D009942:Organometallic Compounds; D012428:Ruthenium