Cavitand Chemistry: Nickel Half‐Sandwich Complexes with Imidazolylidene Ligands Bearing One or Two Resorcinarenyl Substituents

Abstract

Two imidazolium salts, one with a single N-μ 4 -tetramethylenedioxyresorcin[4]arenyl substituent, the other with two, have been used as pro-ligands (LH) for the synthesis of nickel half-sandwich complexes of the type [NiCpClL] (Cp = cyclopentadienyl). NMR and X-ray structural investigations revealed that in both complexes the NiCp moiety is positioned at 4 rue Blaise Pascal,

Synthesis of the First Resorcin[4]arene-Functionalized Triazolium Salts and Their Use in Suzuki–Miyaura Cross-Coupling Reactions

“…Infrared spectra were recorded with a Bruker FTIR Alpha-P spectrometer. Elemental analyses were carried out by the Service de [38], tosyl azide [49], and 2-azido-1,3-dimethoxybenzene [50] were prepared as per the standard procedures found in the literature.…”

“…These were obtained by the reactions of 1 or 2 with [PdCl 2 ] in refluxing pyridine, for 24 h in the presence of K 2 CO 3 and a large excess of KBr in the case of salt 2 (Scheme 2). The observed yields (26% for 9 and 28% for 10) were relatively low, but this was not unusual for reactions carried out with bulky NHC precursors [38,47]. Both complexes were characterized by elemental analysis and 1 H and 13 C NMR spectroscopy.…”

“…As an extension to our studies on the cavity-derived N-heterocyclic carbenes [33][34][35][36][37][38], here, we have described the synthesis of two sterically highly demanding triazolium salts (1 and 2, Figure 1) and their use as a ligand source in the palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl chlorides with arylboronic acids. Very bulky NHCs are currently sought because of their ability to promote oxidative addition or reductive elimination in the Suzuki-Miyaura reactions [39][40][41].…”

“…he resorcin [4]arene-derived triazolium salts 1 and 2 were synthesized, stepwise, accordin quences shown in Scheme 1. The two key steps, namely those leading to intermediates 7 a involved a copper-catalyzed alkyne-azide cycloaddition (CuAAC), betw inarene-azide 6 [38], and an alkyne (with phenyacetylene for the synthesis of triazole 7; yl-resorcinarene 5 for the synthesis of 8), in the presence of CuSO4.5H2O and sodium ascor F. Precursor 5 was obtained from bromo-resorcinarene 3 via a standard palladium-catal ashira cross-coupling with trimethylsilylacetylene. The final methylation steps were ca ith Me3OBF4 for 1 (quantitative yield), and with MeI for 2 (yield 92 %).…”

“…The catalytic solutions were analyzed with a Varian 3900 gas chromatograph, fitted with a WCOT-fused silica column (25 m × 0.25 mm, 0.25 µm film thickness). 5-bromo-4(24),6(10),12(16),18(22)tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene (3) [48], 5-azido-4(24),6(10),12(16),18(22)tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene (6)[38], tosyl azide[49], and 2-azido-1,3-dimethoxybenzene[50] were prepared as per the standard procedures found in the literature.…”