Evaluating a dispersion of sodium in sodium chloride for the synthesis of low-valent nickel complexes

Abstract

The use of a sodium in sodium chloride dispersion is systematically evaluated for the synthesis of nickel(0) and nickel(I) complexes from readily-prepared nickel(II) precursors. A variety of complexes with phosphine and bipyridine-type ligands were accessed, although some reactions were found to produce mixtures of nickel(0) and nickel(I), and yields were highly variable. Several new nickel(I) complexes were obtained, and these were characterised using techniques including NMR spectroscopy, EPR spectroscopy, and single crystal X-ray diffraction analysis.

Synthesis of Nickel(I)–Bromide Complexes via Oxidation and Ligand Displacement: Evaluation of Ligand Effects on Speciation and Reactivity

“…The observed giso value is 2.211, which is also consistent with prior reports. 19,22,57,58 Overall, both EPR spectra are consistent with monomeric d 9 Ni I complexes as observed by SCXRD. Complexes 17 and 18 are the first characterized monomeric t-Bu bpy-bound Ni I complexes.…”

“…The spectrum of a frozen toluene solution containing 17 features no resolved hyperfine splitting and an observed value of gavg = 2.261, which is similar to previous reports of well-defined monomeric (bpy/phen)Ni I (halide) complexes (gavg = 2.19-2.24). 19,22,57,58 For 18, a color change from dark green to red was observed upon freezing in both 2-MeTHF and toluene, and spectra exhibited abnormal lineshape (see SI). Thorough investigation of a chemical process that may be occur ring upon freezing has not been conducted, as spin relaxation for 18 is sufficiently long to observe a room-temperature spectrum.…”

Oxidative Addition of Aryl Halides to a Ni(I)-Bipyridine Complex

“…This holds true for systems bearing ligands from the bipyridine (bpy) or phenanthroline (phen) classes, which are often utilized in synthetic methodologies. [14][15][16][17] In fact, of the few Ni(I)-bpy/phen complexes that have been prepared and structurally characterized, [18][19][20][21][22] only one (a Ni2(I,II) dimer from the Nocera group) has been demonstrated to react with aryl bromides (Figure 1B). 10 Studies by Baran, Diao, and MacMillan/Bird have taken additional key steps towards studying Ni(I)-bpy/phen species generated in situ through reduction (chemically, 20 electrochemically, 23 or radiolytically 24 , respectively).…”