Oxidative addition of aryl halides: routes to mono- and dimetallic nickel amino-bis-phosphinimine complexes

Oxidative addition of an aryl-halide to Ni(COD)(2) in the presence of an equivalent of amino-bis-phosphinimine ligand affords complexes of the form [HN(CH(2)CH(2)N=PPh(3))(2)Ni-Ar][X] (Ar = C(6)H(4)F, C(6)H(5), X = Cl, Br) while the analogous reactions with 2 equivalents of Ni yield the amido-bridged complexes N(CH(2)CH(2)N=PPh(3))Ni(2)Br(3) and N(1,2-C(6)H(4)N=PPh(3))Ni(2)Br(3).     

Mononuclear and dinuclear palladium and nickel complexes of phosphinimine-based tridentate ligands

The tridentate bis-phosphinimine ligands O(1,2-C(6)H(4)N=PPh(3))(2)1, HN(1,2-C(2)H(4)N=PR(3))(2) (R = Ph 2, iPr 3), MeN(1,2-C(2)H(4)N=PPh(3))(2)4 and HN(1,2-C(6)H(4)N=PPh(3))(2)5 were prepared. Employing these ligands, monometallic Pd and Ni complexes O(1,2-C(6)H(4)N=PPh(3))(2)PdCl(2)6, RN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][Cl] (R = H 7, Me 8), [HN(1,2-CH(2)CH(2)N=PiPr(3))(2)PdCl][Cl] 9, [MeN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][PF(6)] 10, [HN(1,2-CH(2)CH(2)N=PPh(3))(2)NiCl(2)] 11, [HN(1,2-CH(2)CH(2)N=PR(3))(2)NiCl][X] (X = Cl, R = iPr 12, X = PF(6), R = Ph 13, iPr 14), and [HN(1,2-C(6)H(4)N=PPh(3))(2)Ni(MeCN)(2)][BF(4)]Cl 15 were prepared and characterized. While the ether-bis-phosphinimine ligand 1 acts in a bidentate fashion to Pd, the amine-bis-phosphinimine ligands 2-5 act in a tridentate fashion, yielding monometallic complexes of varying geometries. In contrast, initial reaction of the amine-bis-phosphinimine ligands with base followed by treatment with NiCl(2)(DME), afforded the amide-bridged bimetallic complexes N(1,2-CH(2)CH(2)N=PR(3))(2)Ni(2)Cl(3) (R = Ph 16, iPr 17) and N(1,2-C(6)H(4)N=PPh(3))(2)Ni(2)Cl(3)18. The precise nature of a number of these complexes were crystallographically characterized.     

Towards Green Ammonia Synthesis through Plasma-Driven Nitrogen Oxidation and Catalytic Reduction

Ammonia is an industrial large-volume chemical, with its main application in fertilizer production. It also attracts increasing attention as a green-energy vector. Over the past century, ammonia production has been dominated by the Haber–Bosch process, in which a mixture of nitrogen and hydrogen gas is converted to ammonia at high temperatures and pressures. Haber–Bosch processes with natural gas as the source of hydrogen are responsible for a significant share of the global CO₂ emissions. Processes involving plasma are currently being investigated as an alternative for decentralized ammonia production powered by renewable energy sources. In this work, we present the PNOCRA process (plasma nitrogen oxidation and catalytic reduction to ammonia), combining plasma-assisted nitrogen oxidation and lean NO_x trap technology, adopted from diesel-engine exhaust gas aftertreatment technology. PNOCRA achieves an energy requirement of 4.6 MJ mol⁻¹ NH₃, which is more than four times less than the state-of-the-art plasma-enabled ammonia synthesis from N₂ and H₂ with reasonable yield (>1 %).     

A deeper insight into strain for the sila‐bi[6]prismane ( ) cluster with its endohedrally trapped silicon atom,

A new family of over‐coordinated hydrogenated silicon nanoclusters with outstanding optical and mechanical properties has recently been proposed. For one member of this family, namely the highly symmetric Si₁₉H₁₂ nanocrystal, strain calculations have been presented with the goal to question its thermal stability and the underlying mechanism of ultrastability and electron‐deficiency aromaticity. Here, the invalidity of these strain energy (SE) calculations is demonstrated mainly based on a fundamentally wrong usage of homodesmotic reactions, the miscounting of atomic bonds, and arithmetic errors. Since the article in question is entirely anchored on those erroneous SE values, all of its conclusions and predictions become without meaning. We provide evidence here that the nanocrystal in question suffers from such low levels of strain that its thermodynamical stability should be largely sufficient for device fabrication in a realistic plasma reactor. Most remarkably, the two “alternative,” irregular isomers explicitly proposed in the aforementioned article are also electron‐deficient, nontetrahedral, ultrastable, and aromatic nicely underlining the universality of the ultrastability concept for nanometric hydrogenated silicon clusters. © 2015 Wiley Periodicals, Inc.     

Equipment Location in Machining Transfer Lines with Multi-spindle Heads

The considered problem appears when a machining line must be configured. It is necessary to define the number of workstations and the number of spindle heads at each workstation to be put in the line in order to produce a given part. This problem is known to be $\mathcal{NP}$ -hard and, as a consequence, the solution time increases exponentially with the size of the problem. A number of pre-processing procedures are suggested in this article in order to decrease the initial problem size and thus shorten the solution time. A new algorithm for calculating a lower bound on the number of required equipment is also presented. A numerical example is given.     

Oxidative Addition at a Carbene Center: Synthesis of an Iminoboryl–CAAC Adduct

The reaction of a cyclic (alkyl)(amino)carbene (CAAC) with dichloro‐ and dibromobis(trimethylsilyl)aminoborane results in the formation of haloiminoborane–CAAC adducts. When the iodo analogue is used, an oxidative addition at the carbene center affords a cationic iminoboryl–CAAC adduct, featuring a boron–nitrogen triple bond. Similar salts are also obtained by halide abstraction from the chloro‐ and bromoiminoborane–CAAC adducts. The reactivity of all of these compounds towards CO₂ is discussed.     

Synthesis and Reactivity of a CAAC–Aminoborylene Adduct: A Hetero‐Allene or an Organoboron Isoelectronic with Singlet Carbenes

A one‐electron reduction of a cyclic (alkyl)(amino)carbene (CAAC)–bis(trimethylsilyl)aminodichloroborane adduct leads to a stable aminoboryl radical. A second one‐electron reduction gives rise to a CAAC–aminoborylene adduct, which features an allenic structure. However, in manner similar to that of stable electrophilic singlet carbenes, this compound activates small molecules, such as CO and H₂.