Organometallic Nickel(II) Complexes Containing Thiolate and Dithiocarbamate Ligands

A mesoionic carbene stabilized nickel(II) hydroxide complex: a facile precursor for C-H activation chemistry

We report the synthesis of a new nickel(II) hydroxide complex 2 supported by a rigid, tridentate triazolylidene-carbazolid ligand. The complex can be accessed in high yields following a simple and stepwise extraction protocol using dichloromethane and aqueous ammonium chloride followed by aqeous sodium hydroxide solution. We found that complex 2 is highly basic, undergoing various deprotonation/desilylation reactions with E-H and C-H acidic and silylated compounds. In this context we synthesized a variety of novel, functionalized nickel(II) complexes with trimethylsilylolate (3), trityl sulfide (4), tosyl amide (5), azido (6), pyridine (7), acetylide (8, 9), fluoroarene (10 & 11) and enolate (12) ligands. We furthermore found that 2 reacts with malonic acid dimethyl ester in a knoevennagel-type condensation reaction, giving access to a new enolate ligand in complex 13, consisting of two malonic acid units. Furthermore, complex 2 reacts with acetonitrile to form the cyanido complex 14. The formation of complexes 13 and 14 is particularly interesting, as they underline the potential of complex 2 in both C-C bond formation and cleavage reactions.

The remarkable propensity for the formation of C–H⋯π(chelate ring) interactions in the crystals of the first-row transition metal dithiocarbamates and the supramolecular architectures they sustain

C–H⋯π(chelate ring) interactions play an important role in assembling first-row transition metal dithiocarbamates in their crystals.

Cationic and neutral Ni(II) complexes containing a non-innocent PNP ligand: formation of alkyl and thiolate species

The synthesis and characterization of a series of cationic and neutral Ni-complexes with the non-innocent PNP(tBu) pincer ligand is discussed. Starting with the dicationic complex , [Ni(PNP(tBu))(NCMe)](BF(4))(2), a small series of dicationic and monocationic Ni(II) complexes has been prepared. Substitution with tert-butyl isocyanide and azide occurs readily in MeCN solution. IR spectroscopy provided a practical handle to access the formal valence state of the ligand. For the mono- and dicationic tert-butyl isocyanide species and the main vibrational bands in the IR spectra were reproduced quantitatively by DFT theoretical calculations, showing good agreement with the experimentally observed Deltanu upon dearomatization of the PNP(tBu) backbone. Using a selective dearomatization-reprotonation methodology the mononuclear Ni-thiolate species and are cleanly generated and their structures have been determined by X-ray crystal structure determination. Alternatively, starting from the monocationic species [Ni(PNP(tBu))Cl]BF(4), neutral alkyl derivatives are easily available in a two-step procedure, and these species have been spectroscopically characterized.