A Neutral, Chiral, Bis(imidazolidine)-Derived NCN-Type Palladium Pincer Complex with Catalytic Activity (original) (raw)
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Journal of Organometallic Chemistry, 2006
New chiral N,N-bidentate ligands derived from substituted 2-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one-2-yl)pyridines have been prepared and characterised by means of 1 H, 13 C NMR spectroscopy and optical rotation. Their Cu(II) complexes were characterized by means of elemental analysis, 1 H NMR spectroscopy and MS. By means of X-ray diffraction, molecular geometry of the complex of 2-(1-methyl-4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one-2-yl)pyridine with copper(II) chloride was determined. The complex exhibits heterochiral dimeric arrangement of two square pyramids with one terminal and one bridge-forming chlorine atoms and two nitrogen atoms in the bases of the pyramids. The tops of these pyramids are formed by the remaining chlorine atoms. The complexes prepared catalyse the Henry reaction with the overall yields of 41-97% and with the maximum enantioselective excess of 19%.
Crystal Growth & Design, 2020
We report herein synthesis, characterization and properties of some metal directed architectures using a new asymmetric, semi-rigid and bis-chelating pyridine-pyrazole based ligand, {N'-(amino (pyrimidin-2-yl)methylene)-3-(pyridin-2-yl)-1H-pyrazole-5-carbohydrazide (H 2 APPC)}. The H 2 APPC ligand forms multinuclear cage complexes with different transition metal salts ranging from discrete mononuclear complex to nonanuclear with different kind of network topology. The semi-rigid ligand molecule not only changes the conformation but also exhibit variable coordination behavior, depending on the metal ions used. For instance, the reaction of manganese salt with H 2 APPC results in a truncated [3×3] grid network whereas the nickel salt forms a highly unusual hexanuclear cage complex. Interestingly, in presence of copper salt, H 2 APPC forms a different kind of structure along with an in-situ generated new ligand. The zinc salts form a mononuclear complex. Most interestingly, reaction with cadmium salts leads to an intriguing [3×3] grid network, with a highly unusual occurrence of multiple variant of coordination environments around the metal centres. It is imperative to note here that above display of metal-directed architectures are quite uncommon for an asymmetric semi-rigid ligand and cadmium complex shows four kind of coordination geometry which is not known in the literature, to the best of our knowledge. The variable temperature magnetic measurements of manganese, nickel and copper complex showed strong antiferromagnetic interaction between the neighboring metal centers. Furthermore, the Cd 9 framework showed promising solvent dependent luminescent properties.
Palladium(II) complexes of chiral tridentate nitrogen pybox ligands
Journal of Organometallic Chemistry, 1996
ABSTRACT A series of mono- and di-cationic palladium(II) complexes containing different chiral tridentate nitrogen ligands, pybox, have been prepared [pybox = 2,6-bis[4′-(S)-iPr (or Ph, or Bz or p-EtOC6H4)oxazoline-2′-yl]pyridine (1–4), respectively]. The molecular structures for two of these, [Pd(CH3CN)(2)](BF4)2 (6) and [Pd(PPh3)(3)](BF4)2 (21g), have been determined by X-ray diffraction and show no major steric hindrance in the fourth coordination position. In connection with the aldol reaction of CNCH2CO2Me with PhCHO, several new isonitrile PdII complexes have also been prepared. It is shown that, under catalytic conditions, the chiral tridentate pybox ligand is completely displaced, thus explaining its failure as a chiral auxiliary. Preparative details for a series of chiral Pd(L)(3)n+(BF4)n (21) complexes [L = 4-methylpyridine, 2,6-dimethylpyridine, 4-methyl aniline, H2NCH2CH(OMe)2, H2NCH2CH2OH, H2N(CH2)5CH3, N3−, HCO2−] Cl−] are given, as are preparative details for some model PdII acetonitrile complexes with chiral phosphorus and nitrogen chelating ligands. For 6, i.e. PdC25H22N4O2B2F8, the crystals are monoclinic with space group P21 (No. 4), a = 13.582(6) Å, b = 13.826(6) Å, c = 14.667(6) Å, β = 97.28(3)°, V = 2732(2) Å3, Z = 4. For 21g, i.e. C43H38B2F8N3O2P2Pd, the crystals are orthorhombic with space group, P212121, a = 10.616(4) Å, b = 16.774(2) Å, c = 23.086(4) Å, V = 4111(3) Å3, Z = 4.
Organometallics, 2008