Novel imidazolium and imidazolinium salts containing the 9-nickelafluorenyl anion – synthesis, structures and reactivity

Abstract

Investigation of the properties of carbene complexes is one of the most important fields of modern coordination chemistry. In this paper, we propose the convenient synthesis of NHC-nickel compounds. The 9-nickelafluorenyllithium complex reacts with imidazolium or imidazolinium salts to afford 9-nickelafluorenyl-NHC salts via ionic metathesis with very good yields (66-92%). These compounds can be isomerised at elevated temperatures to give Ni-NHC complexes with excellent yields (88-91%), probably via nickel mediated hydrogen transfer to the biphenyl moiety. In this reaction, the nickelacyclic ring itself serves as a base in the deprotonation of the carbene precursor. DFT calculations show the thermodynamic instability of the synthesized salts, with Gibbs free energy differences for 1 of -84 kJ mol(-1) at 298 K and -167 kJ mol(-1) at 374 K. The obtained salts and carbene complexes are relatively air and moisture stable in the solid state.

Crystal structure of tris(1,3-dimesityl-4,5-dihydro-1H-imidazol-3-ium) tetrabromidocobaltate(II) bromide chloroform hexasolvate

“…For similar tris(1,3-dimesityl-4,5-dihydro-1H-imidazol-3-ium) structures, see: Arduengo et al (1995); Hagos et al (2008); Santoro et al (2013); Buchalski et al (2015). For synthesis of 2bromo-1,3-dimesityl-4,5-dihydro-1H-imidazol-3-ium bromide, see: Wiggins et al (2012).…”

Fluorescent Chemosensors for Selective and Sensitive Detection of Phosmet/Chlorpyrifos with Octahedral Ni2+ Complexes

“…The metal complexes of imine-linked receptors have been extensively reported because of their pronounced application in research arena of catalysis, biology, mimicking, sensing, and materials science. − These metal complexes have gained the real impulse in last two decades, when materials were explored comprehensively for modulation of surface area, porous nature, and labile metal–ligand interactions. − In this context, multinuclear metal complexes are reported, which mimics the metalloenzyme for their catalytic function such as urease, phosphotase, hemerythrin, catechol oxidase, arginase, ribonuclease reductase. − Similarly, nowadays these metal complexes are intensively being used for sensing of anions, biomolecules, and organophosphate with better optical and electrochemical properties. − The sensing in aqueous medium is a challenging task due to competition between the solvent and guest for receptor binding sites, and the issue is very severe, if the binding is realized with hydrogen bonding. − To address this problem of sensing in aqueous medium, the transition metal complexes have gained good reputation through utilizing electrostatic interaction, vacant d-orbital to form covalent bond or sometimes replacement of labile ligand. , The strategy is explored reasonably; however, many reports are limited to anion sensing only. Contrarily, these activities are applied hardly to warfare chemicals, poisonous materials such as nerve agents, and organophosphates.…”

“…14−16 To address this problem of sensing in aqueous medium, the transition metal complexes have gained good reputation through utilizing electrostatic interaction, vacant dorbital to form covalent bond or sometimes replacement of labile ligand. 17,18 The strategy is explored reasonably; however, many reports are limited to anion sensing only. Contrarily, these activities are applied hardly to warfare chemicals, poisonous materials such as nerve agents, and organophosphates.…”