Improved syntheses of bis(ethynyl)-para-carboranes, 1,12-(RCC)2-1,12-C2B10H10 and 1,10-(RCC)2-1,10-C2B8H8 (R=H or Me3Si)

Fox, Mark A.; Baines, Thomas E.; Albesa‐Jové, David; Howard, Judith A. K.; Low, Paul J.

doi:10.1016/j.jorganchem.2006.05.044

Cited by 12 publications

(9 citation statements)

References 18 publications

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“…Similar phenomena have been observed 'three dimensional' aromatic character [235][236][237], the latter aspect of which has piqued curiosity in these cluster systems as a potential conduit for electronic effects across the cage [238][239][240][241][242][243][244][245]. [246] has made these compounds available for use in the preparation of diethynylcarborane bridged bi- [247,248] and polymetallic [244,245] complexes (Scheme 11).…”

Section: Deceptively Simple: a Ll-carbon Bridgessupporting

confidence: 52%

Twists and turns: Studies of the complexes and properties of bimetallic complexes featuring phenylene ethynylene and related bridging ligands

Low

2013

Coordination Chemistry Reviews

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The concept of a molecular-based electronic technology has been evolving for over 50 years, and the development of molecular designs for such components over this period has drawn heavily on studies of intramolecular charge transfer in mixed-valence complexes and related systems. Recent advances in methods for the assembly and measurement of device characteristics of metal|molecule|metal junctions have brought the realisation of the considerable promise of the area within a tantalisingly close reach. This review presents a selective review of the chemistry, spectroscopic properties and electronic structures of bimetallic complexes [{LxM}(μ-bridge){MLx}]n+ based primarily, but not exclusively, on the Ru(PP)Cp' and Mo(dppe)(η-C7H7) fragments and alkynyl based bridging ligands. The molecular design strategies that lead to a wide spectrum of electronic characteristics in these systems are described. Examples range from weakly coupled mixed-valance complexes through more strongly coupled systems in which the electronic states of the bridging ligand are intimately involved in electron transfer processes to complexes. An argument is made that the latter are better described in terms of redox non-innocent bridging ligands supported by metal-based donor substituents rather than strongly coupled mixed valence complexes. The significance of these results on the further development of metal complexes for use as components within a hybrid molecular electronics technology are discussed.

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Section: Deceptively Simple: a Ll-carbon Bridgessupporting

confidence: 52%

Twists and turns: Studies of the complexes and properties of bimetallic complexes featuring phenylene ethynylene and related bridging ligands

Low

2013

Coordination Chemistry Reviews

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156

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“…Reaction solvents were purified and dried using an Innovative Technology SPS-400 and degassed before use. The compounds [MoBr(dppe)(η-C 7 H 7 )], 1-Me 3 SiCC-1,12-C 2 B 10 H 11 , and 1,12-(HCC) 2 -1,12-C 2 B 10 H 10 , were prepared by literature routes. Other reagents were purchased and used as received.…”

Section: Methodsmentioning

confidence: 99%

Molybdenum Complexes of C,C-Bis(ethynyl)carboranes: Design, Synthesis, and Study of a Weakly Coupled Mixed-Valence Compound

et al. 2010

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The design and study of organometallic mixed-valence complexes is complicated by the mixing of metal d and bridging ligand π orbitals, which often makes the assignment of metal oxidation states ambiguous. However, in the case of complexes based on the cycloheptatrienyl-ligated molybdenum fragment, Mo(dppe)(η-C 7 H 7 ), the strong ring to metal π bonding and metal to ring δ back-bonding interactions stabilize four of the metal d orbitals, while the d z 2 orbital is destabilized by filled-filled interactions with the a-type MO of the C 7 H 7 ring. When the Mo(dppe)(η-C 7 H 7 ) auxiliary is used in conjunction with a 1,12-bis(ethynyl)-1,12-carbaborane-based bridging ligand, a weakly coupled (Robin and Day class II) mixed-valence system, [{Mo(dppe, with well-defined molybdenum oxidation states can be prepared. The near-IR region of [2] þ exhibits three intervalence charge transfer (IVCT) transitions and two lower intensity interconfigurational (or dd) transitions, which have been resolved through spectral deconvolution. The band shape of the lowest energy IVCT transition associated with [2] þ , which arises from electron exchange between the d z 2-type orbitals at the two Mo centers, is in excellent agreement with the predictions of the Hush two-state model for weakly coupled mixed-valence complexes. The halfheight bandwidths of the higher energy IVCT transitions, which arise from transitions between lower lying metal orbitals that have symmetry properties that permit more significant mixing with the bridging ligand, are in less good agreement with the Hush model, due to the breakdown of the two-state approximation through the greater involvement of the bridge-based orbitals in those transitions.

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“…6 This interest can only be expected to increase now that convenient synthetic routes to 10-and 12-vertex diethynyl-p-carboranes 1,10-(Me 3 SiCtC) 2 -1,10-C 2 B 8 H 8 (2a) and 1,12-(Me 3 SiCtC) 2 -1,12-C 2 B 10 H 10 (2b) have been reported (Scheme 1). [7][8][9][10][11][12] The rigid geometry of the diethynyl carboranes together with the potential for the pcarborane cage to mediate electronic effects between groups located at the 1 and 10 (2a) or 1 and 12 (2b) positions has prompted consideration of diethynyl carboranes as conduits for electronic interactions between remote metal centers. 13 Indeed, on the basis of computational results, it has been suggested that the degree of electronic communication between the apical substituents of the 10-vertex carborane cage may be comparable to that of para-substituted benzenes.…”

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Ruthenium Complexes ofC,C‘-Bis(ethynyl)carboranes: An Investigation of Electronic Interactions Mediated by Spherical Pseudo-aromatic Spacers

et al. 2008

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The complexes [Ru(1-C⋮C−1,10-C2B8H9)(dppe)Cp*] (3a), [Ru(1-C⋮C−1,12-C2B10H11)(dppe)Cp*] (3b), [{Ru(dppe)Cp*}2{μ-1,10−(C⋮C)2−1,10-C2B8H8}] (4a) and [{Ru(dppe)Cp*}2{μ-1,12−(C⋮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 Å. 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]+.

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Improved syntheses of bis(ethynyl)-para-carboranes, 1,12-(RCC)2-1,12-C2B10H10 and 1,10-(RCC)2-1,10-C2B8H8 (R=H or Me3Si)

Cited by 12 publications

References 18 publications

Twists and turns: Studies of the complexes and properties of bimetallic complexes featuring phenylene ethynylene and related bridging ligands

Twists and turns: Studies of the complexes and properties of bimetallic complexes featuring phenylene ethynylene and related bridging ligands

Molybdenum Complexes of C,C-Bis(ethynyl)carboranes: Design, Synthesis, and Study of a Weakly Coupled Mixed-Valence Compound

Ruthenium Complexes ofC,C‘-Bis(ethynyl)carboranes: An Investigation of Electronic Interactions Mediated by Spherical Pseudo-aromatic Spacers

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