Isolated Cationic Organometallic Nickel(I) Arene Complexes

Abstract

The NiI salt [Ni(cod)2]+[Al(ORF)4]– {RF = C(CF3)3} is the starting material for ligand exchange reactions with arenes (benzene, mesitylene and hexamethylbenzene) yielding cationic and purely organometallic 19 valence electron [Ni(cod)(arene)]+ complex salts. The reactions are accompanied by fast solution color changes from yellow to intensely green. Single crystal X‐ray structure analysis, EPR, UV/Vis and IR‐spectroscopic investigations confirm the formation of [Ni(cod)(C6Me6)][Al(ORF)4] (2) as well as [Ni(cod)(mes)][Al(ORF)4] (3, mes = mesitylene) with η6‐coordinated arenes and bidentate cod ligands. The reaction with benzene is plausible but remains less characterized. The energetics of these reactions were used to evaluate diverse DFT methods. 16 functionals with and without D3(BJ) dispersion correction failed to describe the reaction energetics correctly. However, correcting the basic reaction energies with a CCSD(T)/TZ→QZ approach and using further isodesmic reactions with inclusion of COSMO‐RS solvation gave reaction energetics in best agreement with all experimental observations.

One to Find Them All: A General Route to Ni(I)–Phenolate Species

“…The Mulliken spin population analysis showed 90% of the spin population localized on Ni, mainly in the d orbitals (see Table S6). This is similar to that of cationic Ni­(COD) 2 + and in line with previously reported metal-centered radicals . The Ni–C COD distances, experimental and calculated, were compared to those of Ni­(COD) 2 + , showing on average shortened bonds (see Table S1).…”

“…This is similar to that of cationic Ni(COD) 2 + and in line with previously reported metalcentered radicals. 60 The Ni−C COD distances, experimental and calculated, were compared to those of Ni(COD) 2 + , showing on average shortened bonds (see Table S1). 56 This is presumably due to the higher back-donation compared to the cationic complex.…”

“…56 Schwab et al reported a minor second component with smaller g z and larger g z strain both in frozen solution and in a powder. 60,61 Because signals with large g strain may go unnoticed in the derivative-mode CW EPR spectra and are better seen in absorption spectra, we acquired a field-swept echo-detected EPR spectrum at 10 K. This spectrum (Figure 1c) showed similar values of the g tensor to those of the frozen solution. 62 It did, however, indeed contain a second component with smaller g z and larger g z strain that in our case turned out to be the majority component (64%).…”