A Heterobimetallic W–Ni Complex Containing a Redox-Active W[SNS]₂ Metalloligand

The tungsten complex W­[SNS]₂ ([SNS]­H₃ = bis­(2-mercapto-4-methylphenyl)­amine) was bound to a Ni­(dppe) [dppe = 1,2-bis­(diphenylphosphino)­ethane] fragment to form the new heterobimetallic complex W­[SNS]₂Ni­(dppe). Characterization of the complex by single-crystal X-ray diffraction revealed the presence of a short W–Ni bond, which renders the complex diamagnetic despite formal tungsten­(V) and nickel­(I) oxidation states. The W­[SNS]₂ unit acts as a redox-active metalloligand in the bimetallic complex, which displays four one-electron redox processes by cyclic voltammetry. In the presence of the organic acid 4-cyanoanilinium tetrafluoroborate, W­[SNS]₂Ni­(dppe) catalyzes the electrochemical reduction of protons to hydrogen coincident with the first reduction of the complex

High Density Alkyl Diamondoid Fuels Synthesized by Catalytic Cracking of Alkanes in the Presence of Adamantane

Alkyl diamondoid fuel mixtures have been prepared under moderate conditions by AlBr₃ catalyzed cracking of nonane and heptane in the presence of adamantane. The fuel mixture prepared with heptane as the alkyl source (HA) contains primarily 1-ethyl-3-methyl adamantane and 1-propyladamantane, while the mixture prepared from nonane (NA) contains primarily C₁₃–C₁₅ alkyl diamondoids. Both fuel mixtures exhibit densities greater than 0.9 g/mL and volumetric net heats of combustion approximately 10 and 6% higher than conventional jet and diesel fuels, respectively. The structural diversity of the fuel blends and presence of multiple branch sites lead to lower viscosities compared to pure alkyl diamondoid fuels. The lower molecular weight blend, HA, exhibits a 40 °C kinematic viscosity of 3.22 mm² s^–1, well within the specification for diesel fuel, and both blends have derived cetane numbers of >42, suggesting that they can be used directly in conventional diesel engines

A Heterobimetallic W–Ni Complex Containing a Redox-Active W[SNS]₂ Metalloligand

The tungsten complex W­[SNS]₂ ([SNS]­H₃ = bis­(2-mercapto-4-methylphenyl)­amine) was bound to a Ni­(dppe) [dppe = 1,2-bis­(diphenylphosphino)­ethane] fragment to form the new heterobimetallic complex W­[SNS]₂Ni­(dppe). Characterization of the complex by single-crystal X-ray diffraction revealed the presence of a short W–Ni bond, which renders the complex diamagnetic despite formal tungsten­(V) and nickel­(I) oxidation states. The W­[SNS]₂ unit acts as a redox-active metalloligand in the bimetallic complex, which displays four one-electron redox processes by cyclic voltammetry. In the presence of the organic acid 4-cyanoanilinium tetrafluoroborate, W­[SNS]₂Ni­(dppe) catalyzes the electrochemical reduction of protons to hydrogen coincident with the first reduction of the complex

Hydrogen-Atom Noninnocence of a Tridentate [SNS] Pincer Ligand

Double deprotonation of bis­(2-mercapto-4-methylphenyl)­amine ([SNS]­H₃) followed by addition to NiCl₂(PR₃)₂ in air-free conditions afforded [SN­(H)­S]­Ni­(PR₃) (<b>1a</b>, R = Cy; <b>1b</b>, R = Ph) complexes, characterized as diamagnetic, square-planar nickel­(II) complexes. When the same reaction was conducted with 3 equiv of KH, the diamagnetic anions K­{[SNS]­Ni­(PR₃)} were obtained (K­[<b>2a</b>], R = Cy; K­[<b>2b</b>], R = Ph). In the presence of air, the reaction proceeds with a concomitant one-electron oxidation. When R = Cy, a square-planar, <i>S</i> = ¹/₂ complex, [SNS]­Ni­(PCy₃) (<b>3a</b>), was isolated. When R = Ph, the bimetallic complex {[SNS]­Ni­(PPh₃)}₂ ({<b>3b</b>}₂) was obtained. This bimetallic species is diamagnetic; however, in solution it dissociates to give <i>S</i> = ¹/₂ monomers analogous to <b>3a</b>. Complexes <b>1</b>–<b>3</b> represent a hydrogen-atom-transfer series. The bond dissociation free energies (BDFEs) for <b>1a</b> and <b>1b</b> were calculated to be 63.9 ± 0.1 and 62.4 ± 0.2 kcal mol^–1, respectively, using the corresponding p<i>K</i>_a and <i>E</i>°′ values. Consistent with these BDFE values, TEMPO^• reacted with <b>1a</b> and <b>1b</b>, resulting in the abstraction of a hydrogen atom to afford <b>3a</b> and <b>3b</b>, respectively