Investigation of catalytic properties of two new orthopalladated complexes supported on montmorillonite: Synthesis, characterization and application in aerobic oxidation of alcohols

Abstract

Two new complexes, [Pd(L1)(C,N)]NO3 (1) and [Pd(L2)(C,N)]NO3 (2) (L1 = 5‐nitro‐1,10‐phenanthroline, L2 = 4‐methyl‐1,10‐phenanthroline, C,N = benzylamine), have been synthesized and characterized using infrared and NMR spectroscopies and elemental analysis. Montmorillonite (MMT‐K10 clay) was used as a solid support for incorporating the cationic part of complexes 1 and 2 to produce catalysts 1 and 2, respectively, as heterogeneous catalysts. Catalyst 1 was identified using powder X‐ray diffraction and scanning and transmission electron microscopies, and the content of palladium obtained from inductively coupled plasma analysis. By changing the electron‐donating group on the L1 ligand with an electron‐withdrawing one, a minor improvement was observed in the catalytic properties. Catalyst 1 showed better efficiency for oxidation of benzyl alcohol in comparison with catalyst 2, so catalyst 1 was used for the aerobic oxidation of alcohols to corresponding aldehydes or ketones without over‐oxidation (with and without bubbling of air). This catalytic system showed high activity towards alcohols under mild conditions. Finally, the reusability of catalyst 1 was investigated with multiple reuses of the supported catalyst in subsequent alcohol oxidation reactions.

A silicon‐labelled amino acid suitable for late‐stage fluorination and unexpected oxidative cleavage reactions in the preparation of a key intermediate in the Strecker synthesis

“…Interestingly, this oxidative cleavage was also observed when using Uemura's palladium catalysed aerobic oxidation, with a 2:1 ratio of 2 : 8 observed by 1 H NMR (Scheme , Entry 6). While unreacted starting material was still the major product in this reaction (64% unreacted 3 was indicated by 1 H NMR), the oxidative cleavage is still notable because it was not reported in other studies on the palladium catalysed aerobic oxidation of homobenzylic alcohols, so this transformation may be dependent on the specific catalyst system. In any case, this is the only example of which we are aware where Uemura's aerobic oxidation leads to oxidative cleavage of a carbon–carbon bond for homobenzylic alcohols.…”

“…Product distributions were determined directly by 1 H NMR spectroscopy for Entries 1-7 and isolated yields are reported for Entries 8-10 SCROGGIE ET AL. | 3 of 6 aerobic oxidation of homobenzylic alcohols, [28][29][30][31][32][33] so this transformation may be dependent on the specific catalyst system. In any case, this is the only example of which we are aware where Uemura's aerobic oxidation leads to oxidative cleavage of a carbon-carbon bond for homobenzylic alcohols.…”

Graphene Oxide-Supported Oxime Palladacycles as Efficient Catalysts for the Suzuki–Miyaura Cross-Coupling Reaction of Aryl Bromides at Room Temperature under Aqueous Conditions

“…Until now, different palladacycles have been immobilized on inorganic and organic supports through covalent or non-covalent interactions [11,12]. Among them, silica-based supports [14][15][16][17][18][19][20][21][22][23][24], organic polymers [19,[25][26][27][28][29][30][31][32][33][34][35][36][37], monolithic supports [38], magnetic nanoparticles [39,40], macrocyclic molecules [41], and Montmorillonite [42,43], are the studied systems. Although these catalysts can be generally reused, a progressive deactivation caused by complex degradation is usually observed, with the reaction products generally being vulnerable to palladium contamination [44].…”