No abstract

The reactions of [Cu(CH3CN)4]PF6 and Cu(ClO4)2 with ((1-benzyl-1H-1,2,3-triazol-4-yl)(pyridin-2-yl)phenylmethanol (Hpytm) in a 1:1 ratio under aerobic conditions afforded [Cu6(pytm)6(SiF6)](SiF6)2 (1) and {[Cu3(pytm)3(MeOH)(ClO4)](ClO4)2}n (2), respectively. Single-crystal X-ray crystallography reveals that both compounds...

Triazole-based ligands, tris (triazolyl)methanol (Htbtm), bis (triazolyl)phenylmethanol (Hbtm), and phenyl (pyridin-2-yl)(triazolyl)methanol (Hpytm), with differences in ligand denticity (i.e., bidentate and tridentate) and type of N donors (i.e., triazole and pyridine) were functionalized onto a silica support to produce the corresponding SiO 2 -L (L = tbtm, btm, pytm). Subsequent reactions with Pd (CH 3 COO) 2 in CH 2 Cl 2 yielded Pd/SiO 2 -L. ICP-MS reveals that Pd loadings are higher with increased N loadings, resulting in the following trend: Pd/SiO 2 -tbtm (0.83 mmol Pd g −1 ) > Pd/SiO 2 -btm (0.65 mmol Pd g −1 )~Pd/SiO 2 -pytm (0.63 mmol Pd g −1 ). Meanwhile, TEM images of the used Pd/SiO 2 -L catalysts after the first catalytic cycle show that the mean size of Pd NPs is highest with Pd/SiO 2 -pytm (8.5 ± 1.5 nm), followed by Pd/SiO 2 -tbtm (6.4 ± 1.6 nm) and Pd/SiO 2 -btm (4.8 ± 1.3 nm). Based on TONs, catalytic studies toward aerobic oxidation of benzyl alcohol to benzaldehyde at 60°C in EtOH showed that Pd/SiO 2 -pytm possessed the most active surface Pd(0) atoms, most likely as a result of more labile properties of the pyridine-triazole ligand compared to tris-and bis (triazolyl) analogs. ICP-MS and TEM analysis of Pd/SiO 2 -btm indicate minimal Pd leaching and similar average Pd NPs sizes after 1 st and 5 th catalytic runs, respectively, confirming that SiO 2 -btm is an efficient Pd NPs stabilizer. The Pd/SiO 2 -btm catalyst was also active toward aerobic oxidation of various benzyl alcohol derivatives in EtOH and could be reused for at least 7 reaction cycles without a significant activity loss.

Trinuclear copper(ii)–triazolyl complexes exhibited higher activities for aerobic alcohol oxidation than the related mononuclear copper(ii) catalyst, most likely due to increased Lewis acidity at copper instead of more reducible copper(ii) centers.