No abstract

No abstract

A new hexahydropyrimidine-based NHC proligand undergoes facile double C–H bond activation to give Pd(ii) and Ni(ii) NHC pincer cationic complexes. The Pd complex catalyzes C–N cross couplings very efficiently.

In this study, a hybrid film bio-nanocomposite material was developed based on the graphene oxide/fungal hyphae (GO-FH) interaction. The developed GO-FH bio-nanocomposite material was used for the removal of hexavalent chromium from aqueous solution. The GO-FH bio-nanocomposite material was prepared by ultrasonic irradiation technique. The synthesized GO-FH bio-nanocomposite material was characterized by XRD, FT-IR, SEM, TEM and TGA. The adsorption experiments were carried out in batch mode to optimize parameters such as pH, adsorbent dosage, initial Cr(VI) ion concentration, contact time and shaking speed. The results indicated that the adsorption of Cr(VI) onto GO-FH bio-nanocomposite material was pH dependant, with the maximum adsorption capacity of 212.76 mg/g occurred at pH 2.0. The adsorption studies followed, Langmuir isotherm and pseudo second order kinetic model. Findings demonstrates that GO-FH bio-nanocomposite material exhibited excellent regeneration performance.

Unsymmetrical pincers have been shown to be better than the corresponding symmetrical pincers in several catalysis reactions. A new unsymmetrical PNN propincer, 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole (1), was synthesized from pyrrole through Mannich bases in a good yield. In addition, the new byproduct 2-(3,5dimethylpyrazolylmethyl)-5-(dimethylaminomethyl)-N-(hydroxymethyl)pyrrole was also isolated. The reaction of 1 with [PdCl 2 (PhCN) 2 ] and Et 3 N in toluene yielded [PdCl-{C 4 H 2 N-2-(CH 2 Me 2 pz)-5-(CH 2 PPh 2 )-κ 3 P,N,N}] (2). The analogous reaction between 1 and [NiCl 2 (DME)] or NiX 2 (X = Br, I) in the presence of NEt 3 in acetonitrile afforded [NiX{C 4 H 2 N-2-(CH 2 Me 2 pz)-5-(CH 2 PPh 2 )-κ 3 P,N,N}] (3; X = Cl, Br, I). All complexes were structurally characterized. The norbornene polymerization behaviors of the unsymmetrical pincer complexes 2 and 3 in the presence of MMAO or EtAlCl 2 were compared with those of the symmetrical pincer complexes chloro[2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrolido]palladium(II) (NNN), chloro[2,5-bis(diphenylphosphinomethyl)pyrrolido]palladium(II), and chloro[2,5-bis-(diphenylphosphinomethyl)pyrrolido]nickel(II) (PNP) at different temperatures.The PNN and NNN complexes exhibited far greater activity on the order of 10 7 g of PNB/mol/h, with quantitative yields in some cases, in comparison to the PNP pincer palladium and nickel complexes. This trend was also supported by the i Pr group substituted PNP nickel and palladium pincer complexes. These polymerization behaviors are explained using steric crowding around the metal atom with the support of NMR studies and suggested that the activity increases as the N pyrazole donor increases. Polymers were characterized by 1 H NMR, IR, TGA, and powder XRD methods.