Synthesis, structures, and reactivity of isomers of [RuCp∗(1,4-(Me2N)2C6H4)]2

[RuCp∗(1,3,5-R3C6H3)]2 {Cp∗ = η5-pentamethylcyclopentadienyl, R = Me, Et} have previously been found to be moderately air stable, yet highly reducing, with estimated D+/0.5D2 (where D2 and D+ represent the dimer and the corresponding monomeric cation, respectively) redox potentials of ca. -2.0 V vs. FeCp2+/0. These properties have led to their use as n-dopants for organic semiconductors. Use of arenes substituted with π-electron donors is anticipated to lead to even more strongly reducing dimers. [RuCp∗(1-(Me2N)-3,5-Me2C6H3)]+PF6- and [RuCp∗(1,4-(Me2N)2C6H4)]+PF6- have been synthesized and electrochemically and crystallographically characterized; both exhibit D+/D potentials slightly more cathodic than [RuCp∗(1,3,5-R3C6H3)]+. Reduction of [RuCp∗(1,4-(Me2N)2C6H4)]+PF6- using silica-supported sodium-potassium alloy leads to a mixture of isomers of [RuCp∗(1,4-(Me2N)2C6H4)]2, two of which have been crystallographically characterized. One of these isomers has a similar molecular structure to [RuCp∗(1,3,5-Et3C6H3)]2; the central C-C bond is exo,exo, i.e., on the opposite face of both six-membered rings from the metals. A D+/0.5D2 potential of -2.4 V is estimated for this exo,exo dimer, more reducing than that of [RuCp∗(1,3,5-R3C6H3)]2 (-2.0 V). This isomer reacts much more rapidly with both air and electron acceptors than [RuCp∗(1,3,5-R3C6H3)]2 due to a much more cathodic D2+/D2 potential. The other isomer to be crystallographically characterized, along with a third isomer, are both dimerized in an exo,endo fashion, representing the first examples of such dimers. Density functional theory calculations and reactivity studies indicate that the central bonds of these two isomers are weaker than those of the exo,exo isomer, or of [RuCp∗(1,3,5-R3C6H3)]2, leading to estimated D+/0.5D2 potentials of -2.5 and -2.6 V vs. FeCp2+/0. At the same time the D2+/D2 potentials for the exo,endo dimers are anodically shifted relative to those of [RuCp∗(1,3,5-R3C6H3)]2, resulting in much greater air stability than for the exo,exo isomer. © 2021 The Royal Society of Chemistry.

Longhi E.1 , Risko C.2 , Bacsa J.3 , Khrustalev V. 4, 5 , Rigin S.4 , Moudgil K.1 , Timofeeva T.V. 4 , Marder S.R. 1, 6, 7, 8, 9 , Barlow S. 1, 6
Royal Society of Chemistry
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  • 1 School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, United States
  • 2 Department of Chemistry, Center for Applied Energy Research (CAER), University of Kentucky, 125 Chemistry-Physics Building, Lexington, KY 40506, United States
  • 3 Crystallography Lab, Emory University, 201 Dowman Drive, Atlanta, GA 30322, United States
  • 4 Department of Chemistry, New Mexico Highlands University, Las Vegas, NM 87701, United States
  • 5 Department of Inorganic Chemistry, Peoples' Friendship University of Russia, Moscow, 117198, Russian Federation
  • 6 Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, CO 80303, United States
  • 7 Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, United States
  • 8 Department of Chemistry, University of Colorado Boulder, Boulder, CO 80303, United States
  • 9 Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden, CO 80401, United States
Ключевые слова
Binary alloys; Dimers; Plants (botany); Redox reactions; Silica; Sodium alloys; % reductions; Air stable; Monomerics; Pentamethylcyclopentadienyl; Property; Redox potentials; Redoxpotential; Sodium-potassium alloy; Synthesised; π-electron donor; Isomers
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