New (η³-Allyl)palladium Complexes with Pyridylpyrazole Ligands:  Synthesis, Characterization, and Study of the Influence of N1 Substituents on the Apparent Allyl Rotation

Abstract

The allylpalladium [Pd(η3-C3H5)(L)](BF4) (L = L1 (1), L2 (2), L3 (3), L4 (4)) complexes with pyridylpyrazole ligands 2-(5-phenyl-1H-pyrazol-3-yl)pyridine (L1), 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L2), 2-(1-octyl-5-phenyl)-1H-pyrazol-3-yl)pyridine (L3), and 2-(5-phenyl-3-(pyridin-2-yl)pyrazol-1-yl)ethanol (L4) were synthesized from the appropriate pyridylpyrazole ligand and [Pd(η3-C3H5)Cl]2 in the presence of AgBF4. The cationic complex 1 was converted into the neutral complex 5 under basic conditions. These complexes were characterized, and the crystal and molecular structure of [Pd(η3-C3H5)(L2)](BF4) (2) was resolved by X-ray diffraction. Also, we have studied the apparent allyl rotation, observed as Hsyn−Hsyn and Hanti−Hanti interconversions. The influences of the solvent, the traces of water, and the N1 substituent have also been studied.

Synthesis, characterization and X-ray crystal structure determination of cyclopalladated [Csp2,N,N′]−, zwitterionic and chelated compounds in the reaction of 3,5-diphenyl-N-alkylaminopyrazole derived ligands with Pd(II)

“…The 1 H, 13 C{ 1 H}NMR, DEPT, COSY, HMQC, and NOESY spectra were recorded in CDCl 3 for 1a, 1c, 2a, and 2c, and in CD 3 CN for 1b and 2b due to the poor solubility of these complexes in CDCl 3 and other solvents.…”

“…In molecule A, the N(13)-H bond length has been geometrically fixed in the refinement (0.91 Å) and the contact parameters between N(13)-H(13)N and Cl (13) are 2.34 Å for HÁ Á ÁCl (13), 3.231(5) Å for N(13)Á Á ÁCl (13) and 164°for N(13)-HÁ Á ÁCl (13). The symmetry code for molecule A is 1/2 À x, 1/2 + y, 1 À z.…”

“…13 C NMR (63 MHz, CDCl 3 ; 298 K): 156.6, 148.6, 132.7, 130.5 (C 3 , C 5 , C 6 , C 12 ), 129. 5-125.7 (C 7-11 , C 13-17 ), 107.5 (C 4 ), 56.5 (C 18 ), 50.6 (C 19 ), 47.6 (N amino (CH 2 CH 3 ) 2 ), 12.2 (N amino (CH 2 CH 3 ) 2 ) ppm.…”

Palladium(II) and platinum(II) complexes with N1-hydroxyethyl-3,5-pyrazole derived ligands

“…Treatment of this b-dione with 2-hydroxyethylhydrazine in absolute ethanol at room temperature during 16 h produced two regioisomers, 2-(5-methyl-3-phenyl-1H-pyrazol-1-yl)ethanol (L1) and 2-(3-methyl-5-phenyl-1H-pyrazol-1-yl)ethanol (L2) in a 98% yield (Scheme 1). The higher reaction time required for this synthesis compared with similar ones described in the literature is probably due to both electronic and steric hindrance effects of the methyl group [10]. The separation of the two regioisomers was carried out by silica column chromatography using ethyl acetate as eluent.…”

β‐Protic Pyrazole and N‐Heterocyclic Carbene Complexes: Synthesis, Properties, and Metal–Ligand Cooperative Bifunctional Catalysis

“…Among chelating protic pyrazole ligands, the N-N chelate derivatives such as pyridylpyrazoles are most extensively studied. [10] Representative examples (8-10) of square-planar, [11][12][13][14][15][16][17][18] octahedral, [19] and half-sandwichtype [20,21] pyridylpyrazole complexes are shown here. In addition, a number of osmium, iridium, and platinum complexes bearing the deprotonated pyridylpyrazolato ligands have been synthesized, motivated by their luminescent properties.…”