Nickel(II) allyl complexes with anionic N-heterocyclic carbene-borate ligands

• Published in: Journal of organometallic chemistry 2020-07, Vol.918, p.121311, Article 121311
• Main Authors: Frosch, Jenni, Freytag, Matthias, Jones, Peter G., Tamm, Matthias
• Format: Article
• Language: English
• Subjects: Allyl complexes; Boranes; Carbonyl complex; N-Heterocyclic carbenes; Nickel; Phosphines
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2020.121311

Deprotonation of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (IDipp) with n-butyllithium at the 4-position and addition of B(C6F5)3 afforded the lithium-carbene borate complex [(WCA-NHC)Li(toluene)] with a weakly coordinating anionic (WCA) moiety. The reaction of the lithiocarbene with the dimeric allyl complex [(η3-C3H5)Ni(μ-Cl)]2 in tetrahydrofuran (THF) afforded the chloronickelate complex [Li(THF)n][(WCA-IDipp)NiCl(η3-C3H5)] (1 ≤ n ≤ 3), which was used to generate the complex [(WCA-IDipp)Ni(η3-C3H5)], which is expected to achieve stabilization through an intramolecular arene-metal interaction (“π-face donation”) involving the N-aryl groups of the carbene ligand, by elimination of LiCl in toluene solution. The labile complex [(WCA-IDipp)Ni(η3-C3H5)], which undergoes decomposition by C–H activation and/or reductive elimination, can be stabilized by addition of carbon monoxide or phosphines to form novel neutral complexes of the type [(WCA-IDipp)NiL(η3-C3H5)] (L = CO, PMe3, PMe2Ph, PMePh2). [Display omitted] •Anionic N-heterocyclic carbenes stabilize neutral nickel(II) allyl complexes.•A rare example of a stable nickel(II) carbonyl complex can be isolated.•Decomposition of nickel(II) allyl complexes occurs through C–H activation and/or reductive elimination.