Ni Halides Research Articles

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2)–C(sp3)Coupling Reactions

AbstractA number of new transition metal catalyzed methods for the formation of C(sp2)–C(sp3) bonds have recently been described. These reactions often utilize bidentate polypyridyl‐ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl‐ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2)–C(sp3) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2)–C(sp3) coupling through stoichiometric studies and also explore their catalytic activity.

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2 )-C(sp3 )Coupling Reactions.

A number of new transition metal catalyzed methods for the formation of C(sp2 )-C(sp3 ) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2 )-C(sp3 ) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2 )-C(sp3 ) coupling through stoichiometric studies and also explore their catalytic activity.

Trinuclear Nickel Complexes with Metal-Arene Interactions Supported by Tris- and Bis(phosphinoaryl)benzene Frameworks.

Triphosphine and diphosphine ligands with backbones designed to facilitate metal-arene interactions were employed to support multinuclear Ni complexes. Di- and trinuclear metal complexes supported by a triphosphine containing a triarylbenzene linker display diverse metal-arene binding modes. Multinuclear Ni halide complexes were isolated with strongly interacting metal centers bound to opposite faces of the coordinated arene. Upon reaction of the trinickel diiodide complex, 2, with disodium tetracarbonylferrate, a cofacial triangulo nickel(0) complex, 4, was isolated. The Ni03 cluster motif can also be supported by a para-terphenyldiphosphine, where a terminal carbon monoxide ligand replaces the third phosphine donor. All multinuclear complexes feature strong metal-arene interactions, demonstrating the use of an arene as a versatile ligand design element for small clusters.

Coulomb correlation energy versus covalence in transition-metal compounds

We have performed optical and photoemission studies on Mott–Hubbard and charge transfer insulators with formal ionic configurations 3d 3 (CrCl 3, CrBr 3) and 3d 8 (NiCl 2, NiBr 2, NiI 2). The photoemission spectra have been analyzed in terms of a cluster model leading to estimates of the on-site Coulomb repulsion energy, charge transfer energy and hybridization energy parameters. The ionicity parameter f i in Cr and Ni compounds has been calculated by the means of the Phillips–Van Vechten theory: its value is about 0.80 in Cr halides, and it varies from 0.70 in NiI 2 to 0.80 in NiCl 2 in Ni halides. We have also considered the ionicity scale f i DT of the dielectric theory. The two scales allow a good understanding of the chemical bond character and electron correlation in these materials.

Electrical properties of liquid NiTe alloys with Ni halides

Liquid NiTe has a large electrical conductivity of 5700 Ω −1 cm −1 at the melting point. The decrease in the conductivity on the NiTe side is about 140 and 230 Ω −1 cm −1 with the addition of 1 mol% NiCl 2 and NiI 2, respectively. Liquid NiTe and molten NiI 2 were found to be miscible in all proportions. Molten NiI 2 has a conductivity of 35 Ω −1 cm −1 at 950 °C. The electrical conductivity on the NiI 2 side increases gradually with the addition of NiTe. The composition dependence of the thermoelectric power of molten NiTe–NiI 2 mixtures increases gradually from −3 μV/K on the NiTe side to 37.5 μV/K on the NiI 2 side. The composition dependence of the conductivity and thermoelectric power for molten NiTe–NiI 2 mixtures was analyzed by electronic model of liquid semiconductors.

Electrochemical reduction of Ni(II) phosphine and phosphite complexes

1. The formation of stable pentacoordinated complexes of Ni halides and nitrate has been demonstrated in the presence of a 100-fold excess of the phosphines and phosphites in ethanol and CH3CN. 2. A wave shift to a region of less negative potentials in the displacement of complex-formation equilibrium by an excess concentration of organic ligand was determined by the greater stability of the [NiL4] complexes formed on reduction. 3. Two-electron quasireversible reduction of the compounds studied leads to formation of Ni(0) phosphine and phosphite complexes with a coordination number of 4 and 3.