Microwave-assisted synthesis of (N-heterocyclic carbene)Ni(Cp)Cl complexes

Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis

“…In particular, the compounds (49) [291] and (172−175) [292] were used for the anaerobic oxidation of secondary alcohols to ketones.…”

Benzothiazole Nickelation: An Obstacle to the Catalytic Arylation of Azoles by Cyclopentadienyl Nickel N-Heterocyclic Carbene Complexes

“…Thus, for instance, the 1 H NMR spectrum of 7 no longer displays the H(2) proton of benzothiazole, but displays the H(5) and H(6) protons as two Catalysts 2019, 9, 76 4 of 10 apparent triplets at 7.12 and 6.98 ppm, as seen in the spectra of the catalytic attempts (vide supra), and the H(4) and H(7) protons as two doublets at 7.58 and 7.51 ppm ( Figure S4). The Cp and IMes protons are found at values that are typical for NiCp(IMes) compounds [27][28][29][30][31][32][33][35][36][37]. Regarding the 13 C{ 1 H} NMR spectrum, the C(2) carbon of the benzothiazolyl moiety is observed at 176.0 ppm, which is significantly downfield compared to the corresponding carbon of free benzothiazole (153.8 ppm) [42], and thus confirms its metallation ( Figure S5) [23].…”

“…35(9) • ) [34] and [NiCp(IMes)(IMe)](BF 4 ) (96.91(11) • ) [47]. Finally, when one takes into account the plane formed by the Cp centroid, C(1), and C(2), the nickel atom is almost in a planar environment ( Table 2, last entry), as is typically observed in similar two-legged piano-stool CpNi(NHC) complexes [27][28][29][30][31][32][33]35]. Table 2.…”

“…We therefore wondered whether Cp † Ni [Cp † = Cp (η 5 -C 5 H 5 ), Cp* (η 5 -C 5 Me 5 )] complexes bearing a monodentate NHC ligand as well as a readily labile halide or acetonitrile ligand could catalyze such direct biaryl couplings. This family of complexes has indeed been proven to constitute a very versatile class of pre-catalysts [27][28][29][30][31][32][33] that notably catalyze the α-arylation of ketones [34]. Herein, we report our findings, which show that, under the typical conditions used for the direct coupling of azoles with aryl halides or pseudo-halides (i.e.…”

“…Four half-sandwich Ni(NHC) complexes, which have already been demonstrated to catalyze a variety of reactions [27][28][29][30][31][32][33], were chosen for the present study: complexes 3 [35][36][37] and 4 [27,37] bearing a Cp ring, a chloride and, respectively, the 1,3-bis(2,4,6-trimethylphenylimidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenylimidazol-2-ylidene (IPr) as NHC ligands, complex 5 [38], the Cp* analogue of 3, and complex 6 [29], the cationic analogue of 3 that bears a labile acetonitrile ligand instead of a chloride ( Figure 1). Catalysts 2019, 9, x FOR PEER REVIEW 2 of 11 [5,9,10,12,24]), apart from a Cp* derivative which shows a little activity with aryl iodides, these complexes form a stable C(2)-nickelated azolyl complex that arrests any further reactivity.…”