Preparation and structures of a series of phosphorus-free Nickel(II) diamine complexes and their applications in hydrogenation of acetophenone

Transfer Hydrogenation of Ketones Catalyzed by Symmetric Imino-N-heterocyclic Carbene Co(III) Complexes

The synthesis of new moisture-sensitive imine-functionalized N-heterocyclic carbene (NHC) precursor salts [1-(2-[(hydroxyl-benzylidene)-amino]-ethyl)-3-R-3H-imidazole-1-ium bromide; R = methyl (1a), ethyl (1b), and benzyl (1c)] is reported. Subsequent deprotonation of 1a-c and coordination of the in situ generated NHC ligands to CoBr₂ led to the isolation of air-stable six-coordinate Co(III) complexes 2a-c, respectively. All the salts and complexes were fully characterized. Single-crystal X-ray analysis of 2a and 2c showed octahedral Co centers hexacoordinated to two NHC carbons, two imine nitrogen atoms, and two phenolate oxygens in the form [C^N^O(Co³⁺)C^N^O]. The complexes were used in the catalytic transfer hydrogenation (CTH) of a range of ketones in 2-propanol as the solvent and hydrogen donor. Based on a low catalyst concentration of 0.4 mol %, significant conversions in the range of 70-99% were recorded at high turnover frequencies up to 1635 h^-1. A mechanism to account for the steps involved in the CTH of cyclohexanone by complex 2a is proposed and supported by data from cyclic voltammetry, low-resolution mass spectrometry, UV, and IR spectroscopic techniques.

Di-chlorido-bis-[2-(pyridin-2-yl-κN)-1H-benzimidazole-κN 3]nickel(II) monohydrate

In the title complex, [NiCl2(C12H9N3)2]·H2O, a divalent nickel atom is coordinated by two 2-(pyridin-2-yl)-1H-benzimidazole ligands in a slightly distorted octa-hedral environment defined by four N donors of two N,N'-chelating ligands, along with two cis-oriented anionic chloride donors. The title complex crystallized with a water mol-ecule disordered over two positions. In the crystal, a combination of O-H⋯Cl, O-H.·O and N-H⋯Cl hydrogen bonds, together with C-H⋯O, C-H⋯Cl and C-H⋯π inter-actions, links the complex mol-ecules and the water mol-ecules to form a supra-molecular three-dimensional framework. The title complex is isostructural with the cobalt(II) dichloride complex reported previously [Das et al. (2011 ▸). Org. Biomol. Chem. 9, 7097-7107].

Transfer hydrogenation of aldehydes and ketones catalyzed using an aminophosphinite POCNH pincer complex of Ni(ii)

(POCN^H)NiBr catalyzes the transfer hydrogenation of aldehydes and ketones in iPrOH. The reactions tolerate alkenes, esters, amides, nitriles, and heterocycles and proceed via the metal–ligand cooperative mechanism through (POCN)Ni^II species.

Multiple deprotonation of primary aromatic diamines by LiAlH4

Reaction of LiAlH₄with 1,2-phenylenediamine (1H₄) in THF gives [{Al(1H₂)}₂{Al(1H)₂}₂][Li(THF)₂]₄, containing the largest aluminate of its type so far reported.