ABSTRACT
Ru nanoclusters (average diameter = 1.3 ± 0.3 nm) were successfully prepared by using a Ru3 cluster Ru3O(CH3COO)6(H2O)3·(CH3COO) grafted on a pyridine-functionalized SiO2 surface. The pyridine moiety dispersed on the SiO2 surface spread the Ru3 cluster, controlling its surface density, and the nanoclusterization of the Ru cluster proceeded on the surface. The structures of the Ru nanoclusters were characterized by means of elemental analysis; thermogravimetric analysis; FT-IR, UV/vis, and solid-state NMR spectroscopy; BET analysis; X-ray photoelectron spectroscopy; X-ray diffraction; transmission electron microscopy; and Ru K-edge X-ray absorption fine structure analysis. It was found that the catalytic activity for the selective oxidation of alcohol to the corresponding aldehyde using O2 highly depended on the dispersion and structures of the Ru particles, and the Ru nanocluster was found to be efficient in the selective oxidation of a variety of alcohols.
Subject(s)
Alcohols/chemistry , Aldehydes/chemical synthesis , Metal Nanoparticles/chemistry , Organometallic Compounds/chemistry , Ruthenium/chemistry , Silicon Dioxide/chemistry , Aldehydes/chemistry , Molecular Structure , Oxidation-Reduction , Particle Size , Pyridines/chemistry , Surface PropertiesABSTRACT
Eight bis(salicylaldiminato)tin(II) complexes have been synthesized from the reaction of Sn[N(SiMe(3))(2)](2) and 2 equiv of the corresponding ligands at room temperature. The ligands, synthesized from salicylaldehyde and amines, were designed to have different electronic and steric properties using different amines to synthesize the tin(II) complexes as aniline (2a), 2,6-dimethylaniline (2b), 2,6-diisopropylaniline (2c), 4-methoxyaniline (2d), 4-trifluoromethylaniline (2e), methylamine (2g), and tert-butylamine (2h). Ligand variation at the salicyl group synthesized from 4-bromosalicylaldehyde and 2,6-diisopropylaniline was used to form complex 2f. Complex 2c was characterized crystallographically. All catalysts were active for the neat polymerization of L-lactide at 115 °C. At a lactide : Sn molar ratio of 10 : 1, cyclic polylactide (PLA) was obtained as demonstrated by (1)H NMR and mass spectrometry. Addition of 1 equiv of benzyl alcohol in the polymerization produced linear PLA. At a higher lactide : Sn molar ratio of 200 : 1, high molecular weight PLAs with M(n) up to 132,200 Daltons were obtained. Results from GPC coupled with light scattering detector and viscometer suggested that they are cyclic PLA. The order of reactivity based on conversion was determined to be 2c < 2b < 2a in accordance with lower steric hindrance. For electronic contribution, the order of 2e < 2a < 2d was observed in agreement with the increasing electron donation of the ligands. Complex 2g having the smallest substituents was found to be the most active catalyst.
Subject(s)
Organometallic Compounds/chemistry , Polyesters/chemistry , Tin/chemistry , Catalysis , Coordination Complexes/chemistry , LigandsABSTRACT
A series of bis(amidinate) tin(II) complexes is synthesized and shown to rapidly polymerize ε-caprolactone (ε-CL) in the presence and absence of benzyl alcohol giving high-molecular-weight poly(ε-CL) (M(n) up to 160,600 Da). Ligands having electron donating groups were found to accelerate the polymerization by making the complex more nucleophilic.
