Synthesis, Reactivity, and Catalytic Application of a Nickel Pincer Hydride Complex

The nickel­(II) hydride complex [(^MeN₂N)­Ni-H] (<b>2</b>) was synthesized by the reaction of [(^MeN₂N)­Ni-OMe] (<b>6</b>) with Ph₂SiH₂ and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. <b>2</b> was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N–H reductive elimination to give ^MeN₂NH and nickel particles. The second pathway was intermolecular, with H₂, nickel particles, and a five-coordinate Ni­(II) complex [(^MeN₂N)₂Ni] (<b>8</b>) as the products. <b>2</b> reacted with acetone and ethylene, forming [(^MeN₂N)­Ni-O^<i>i</i>Pr] (<b>9</b>) and [(^MeN₂N)­Ni-Et] (<b>10</b>), respectively. <b>2</b> also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(^MeN₂N)­Ni-Cl] (<b>1</b>) as catalyst, NaO^<i>i</i>Pr or NaOMe as base, and Ph₂SiH₂ or Me­(EtO)₂SiH as the hydride source. The catalysis appears to operate via a radical mechanism

Synthesis, Reactivity, and Catalytic Application of a Nickel Pincer Hydride Complex

The nickel­(II) hydride complex [(^MeN₂N)­Ni-H] (<b>2</b>) was synthesized by the reaction of [(^MeN₂N)­Ni-OMe] (<b>6</b>) with Ph₂SiH₂ and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. <b>2</b> was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N–H reductive elimination to give ^MeN₂NH and nickel particles. The second pathway was intermolecular, with H₂, nickel particles, and a five-coordinate Ni­(II) complex [(^MeN₂N)₂Ni] (<b>8</b>) as the products. <b>2</b> reacted with acetone and ethylene, forming [(^MeN₂N)­Ni-O^<i>i</i>Pr] (<b>9</b>) and [(^MeN₂N)­Ni-Et] (<b>10</b>), respectively. <b>2</b> also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(^MeN₂N)­Ni-Cl] (<b>1</b>) as catalyst, NaO^<i>i</i>Pr or NaOMe as base, and Ph₂SiH₂ or Me­(EtO)₂SiH as the hydride source. The catalysis appears to operate via a radical mechanism

Copper-Catalyzed Alkylation of Benzoxazoles with Secondary Alkyl Halides

Copper-catalyzed direct alkylation of benzoxazoles using nonactivated secondary alkyl halides has been developed. The best catalyst is a new copper(I) complex (<b>1</b>), and the reactions are promoted by bis[2-(<i>N</i>,<i>N</i>-dimethylamino)ethyl] ether

Activation of Nitrous Oxide by Dinuclear Ruthenium Complexes

The dinuclear Ru­(II) complexes (arene)­Ru­(μ-Cl)₃RuCl­(C₂H₄)­(PCy₃) (arene = <i>p</i>-cymene or 1,3,5-C₆H₃<i>i</i>Pr₃) react with N₂O under mild conditions to give OPCy₃ and the trinuclear complexes (arene)­Ru­(μ-Cl)₃Ru­(μ-Cl)₃Ru­(arene). The N-heterocyclic carbene complex (<i>p</i>-cymene)­Ru­(μ-Cl)₃RuCl­(C₂H₄)­(IMes) (IMes = 1,3-dimesitylimidazol-2-ylidene), on the other hand, reacts with N₂O to give a mixed-valence Ru­(II)/Ru­(III) complex with a chelating alkoxy ligand. Dinitrogen complexes were identified as intermediates in all reactions. At elevated temperature, the carbene complex (<i>p</i>-cymene)­Ru­(μ-Cl)₃RuCl­(C₂H₄)­(IMes) is able to catalyze the oxidation of alcohols with N₂O

Copper-Catalyzed Alkylation of Benzoxazoles with Secondary Alkyl Halides

Copper-catalyzed direct alkylation of benzoxazoles using nonactivated secondary alkyl halides has been developed. The best catalyst is a new copper(I) complex (<b>1</b>), and the reactions are promoted by bis[2-(<i>N</i>,<i>N</i>-dimethylamino)ethyl] ether

Reactions of Grignard Reagents with Nitrous Oxide

The chemical activation of nitrous oxide (N₂O) can be achieved by organocalcium, organosodium, and organolithium compounds. Grignard reagents, on the other hand, are believed to be inert. We demonstrate that this generalization is not correct. Some aliphatic Grignard reagents undergo a rapid conversion when subjected to an atmosphere of N₂O. Hydrazones are the main reaction products

Insertion of Zerovalent Nickel into the N–N Bond of N‑Heterocyclic-Carbene-Activated N₂O

Metal-mediated cleavage of the N–N bond is a rarely observed phenomenon in the chemistry of nitrous oxide (N₂O). We demonstrate that, upon activation of N₂O with N-heterocyclic carbenes, zerovalent nickel is able to insert into the N–N bond to give nitrosyl complexes

One-Pot Synthesis of Trisubstituted Triazenes from Grignard Reagents and Organic Azides

A simple and versatile method for the preparation of linear, trisubstituted triazenes is reported. The procedure is based on the reaction of Grignard reagents with 1-azido-4-iodobutane or 4-azidobutyl-4-methylbenzenesulfonate. These organic azides enable the regioselective formation of triazenes via an intramolecular cyclization step. The new method can be used for the preparation of aryl, heteroaryl, vinyl, and alkyl triazenes. The synthetic utility of vinyl triazenes is demonstrated by acid-induced C–N, C–O, C–F, C–P, and C–S bond-forming reactions

Pattern-Based Sensing of Peptides and Aminoglycosides with a Single Molecular Probe

A coumarin-based molecular probe can be used for the sensing of peptides and aminoglycoside antibiotics. The probe reacts with the primary amine group(s) of the analytes to give a mixture of covalent adducts with distinct colors. Each analyte gives rise to a characteristic UV–vis spectrum. A pattern-based analysis of the spectra allows identifying structurally related analytes. Furthermore, it is possible to obtain information about the quantity and the purity of the analytes

Adducts of Nitrous Oxide and N‑Heterocyclic Carbenes: Syntheses, Structures, and Reactivity

N-Heterocyclic carbenes (NHCs) react at ambient conditions with nitrous oxide to give covalent adducts. In the crystal, all compounds show a bent N₂O group connected via the N-atom to the former carbene carbon atom. Most adducts are stable at room temperature, but heating induces decomposition into the corresponding ureas. Kinetic experiments show that the thermal stability of the NHC–N₂O adducts depends on steric as well as electronic effects. The coordination of N₂O to NHCs weakens the N–N bond substantially, and facile N–N bond rupture was observed in reactions with acid or acetyl chloride. On the other hand, reaction with tritylium tetrafluoroborate resulted in a covalent modification of the terminal O-atom, and cleavage of the C–N₂O bond was observed in a reaction with thionyl chloride. The coordination chemistry of IMes–N₂O (IMes = 1,3-dimesitylimidazol-2-ylidene) was explored in reactions with the complexes CuOTf, Fe­(OTf)₂, PhSnCl₃, CuCl₂, and Zn­(C₆F₅)₂. Structural analyses show that IMes–N₂O is able to act as a N-donor, as an O-donor, or as a chelating N,O-donor. The different coordination modes go along with pronounced electronic changes as evidenced by a bond length analysis