Transient Formation and Reactivity of a High-Valent Nickel(IV) Oxido Complex

Abstract

A reactive high-valent dinuclear nickel(IV) oxido bridged complex is reported that can be formed at room temperature by reaction of [(L)2Ni(II)2(μ-X)3]X (X = Cl or Br) with NaOCl in methanol or acetonitrile (where L = 1,4,7-trimethyl-1,4,7-triazacyclononane). The unusual Ni(IV) oxido species is stabilized within a dinuclear tris-μ-oxido-bridged structure as [(L)2Ni(IV)2(μ-O)3]2+. Its structure and its reactivity with organic substrates are demonstrated through a combination of UV–vis absorption, resonance Raman, 1H NMR, EPR, and X-ray absorption (near-edge) spectroscopy, ESI mass spectrometry, and DFT methods. The identification of a Ni(IV)-O species opens opportunities to control the reactivity of NaOCl for selective oxidations.

Aerobic C–C and C–O bond formation reactions mediated by high-valent nickel species

“…Overall, these results are very promising, suggesting that with an appropriately tailored multidentate ligand the corresponding organometallic Ni complexes can be oxidized with mild oxidants such as O 2 and H 2 O 2 and promote C-C and C-heteroatom bond formation reactivity that is usually possible only under stringent anaerobic and anhydrous conditions. Interestingly, high-valent Ni-oxo species supported by the multidentate amine ligands have also been reported recently, 56 lending support to the transient species proposed above. It is also important to note that similar reactivity with O 2 and H 2 O 2 has been observed previously for both Pt and Pd complexes.…”

Preparation and Characterisation of a Bis‐μ‐Hydroxo‐NiIII2 Complex

“…Riordan reported the first examples of bis‐μ‐oxo‐Ni III 2 supported by thiolate ligands . More recently, Browne and co‐workers reported the first example of a metastable dinuclear tris‐μ‐oxido‐Ni IV complex . To the best of our knowledge no hydroxide‐bridged high‐valent Ni 2 complexes have been reported to date, and there is limited insight into the reactivity properties of any hydroxide bridged high‐valent oxidants.…”

“…[13] More recently,B rowne and co-workers reported the first exampleo fametastable dinuclear tris-moxido-Ni IV complex. [14] To the best of our knowledge no hydroxide-bridged high-valent Ni 2 complexes have been reportedt od ate, and there is limited insight into the reactivity properties of any hydroxide bridged high-valent oxidants. Herein, we report the synthesis, characterisation, and reactivity properties of bis-m-hydroxo-Ni II Ni III and bis-m-hydroxo-Ni III 2 complexes.…”

Density functional approximations for consistent spin and oxidation states of oxoiron complexes

“…In modern chemistry, computer modeling is a prominent means to reduce the cost associated with synthesis, testing, application, and can serve as a tool to explain experimental data in more detail. Furthermore, the combination of accurate structure prediction and reliable computational spectroscopy makes that computational chemistry is nowadays one of the major techniques used for characterization of chemical species …”

“…Various oxoiron complexes have been examined, however questions remain about their structure, oxidation state and spin state, and the effect these have on their properties and reactivity . Many of these uncertainties have been clarified through the use of DFAs, where a direct match between spectroscopic features, spin states and structures could be made . One widely discussed example is posed by a fascinating Sc 3+ ‐capped oxoiron complex [(TMC)(Fe III/IV ‐O‐Sc III )(OTf) 4 (OH x )] (TMC = 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane), synthetized by Fukuzumi, Nam and co‐workers and characterized by X‐ray crystallography .…”