Two Copper-Containing Polyoxometalate-Based Metal–Organic Complexes as Heterogeneous Catalysts for the C–H Bond Oxidation of Benzylic Compounds and Olefin Epoxidation

Abstract

Using a one-pot assembly method, two novel copper-containing Keggin-type polyoxometalates (POMs)-based m e t a l − o r g a n i c c o m p l e x e s , t h a t i s , [Cu II 2 (pbba) 2 NO 3 − (H 2 O) 2 (PW 12 O 40 )]•3H 2 O [PW 12 -Cu-pbba, H 2 pbba = 1,1′-(1,4-phenylene-bis(methylene))-bis(pyridine-3-carboxylic acid)] and [Cu II 2 (pbba) 2 (H 2 O) 2 (GeW 12 O 40 )]•3H 2 O (GeW 12 -Cu-pbba), were successfully synthesized. These two complexes are isostructural, differing only in their POM components. They are applicable as heterogeneous catalysts for the C−H bond oxidation of benzylic compounds and olefin epoxidation under mild conditions, with oxygen as the oxidant and isobutyraldehyde as the coreductant. The catalytic activity of PW 12 -Cu-pbba was superior to that of GeW 12 -Cu-pbba. Under the optimal conditions, PW 12 -Cu-pbba catalyzed the oxidation of indane into 1-indanone with an 81% yield and >99% selectivity within 48 h. As heterogeneous catalysts, both complexes demonstrated excellent recoverability and high stability and could be stably reused five times without significant activity loss.

Enhanced Catalytic Activity of a Copper(II) Metal–Organic Framework Constructed via Semireversible Single-Crystal-to-Single-Crystal Dehydration

“…Interestingly, one oxygen atom (μ 2 -O5W) forms an unusual bridge between two Cu­(II) centers with bond distances 1.944(5) and 2.507(5) Å (Tables and S8), creating a pentacoordinate geometry. The distance between two Cu­(II) spheres bridged by H 2 O as a ligand is reported to be between 2.841 and 3.768 Å. − The lengths of Cu–O carboxylate bonds range from 1.951(5) to 2.546(5) Å, which is within the normal range. , It is noticeable that the bond length of Cu–O basal elongated (typical Jahn–Teller distortion) while that of Cu–O apical shortened when the aqua molecule bridged the two Cu­(II) centers in 3 . As shown in Table S8, the cis and trans (∠O–Cu–O) angles are in the range of 56.5(2)–104.4(2)° and 164.6(2)–168.9(2)°, respectively.…”

Structural Regulation of Two Polyoxometalate-Based Metal–Organic Frameworks for the Heterogeneous Catalysis of Quinazolinones

“…Therefore, POMOF materials could be regarded as one of the ideal candidates for efficient heterogeneous catalysts. Several relative POMOF materials with diverse constitutions and configurations have been reported − and further explored their catalytic abilities mainly focused on photocatalytic or electrocatalytic hydrogen evolution, CO 2 reduction, , oxidation of alkylbenzenes to aldehydes, , olefin epoxidation, or oxidation of silanes. , The catalytic synthesis of quinazolinones and their derivatives based on POMOF catalysts still remains large to explore.…”

Iron nitrate and 4-OH-TEMPO-cocatalyzed aerobic oxidation of isochromans

“…2 Direct aerobic oxidation of isochromans was reported; however, a high temperature of 80 or 140 °C was required (Scheme 1a). 3 Recently, photoredox catalysts, 4 electrochemical catalysts, 5 acid catalysts, 6 organocatalysts, 7 nitroxyl catalysts, 8 doped carbon materials, 9 and transition metal catalysts 10 have been employed in the aerobic oxidation of isochromans. Iron-based catalysis has received much attention because of its natural abundance, low cost and environmentally friendly nature (Scheme 1b): 11 Xiao and coworkers reported Fe(OTf) 2 with a PyBisulidine ligand with low conversion with 1,1′-oxidi-isochromans as the byproducts; 11 a in 2017, Shen et al .…”