Zn(II)-to-Cu(II) Transmetalation in an Amide Functionalized Complex and Catalytic Applications in Styrene Oxidation and Nitroaldol Coupling

Abstract

The mononuclear zinc(II) complex cis-[ZnL2(H2O)2] (1; L = 4-(pyridin-3-ylcarbamoyl)benzoate) was synthesized and characterized. By soaking crystals of 1 in a mixture of DMF-H2O solution containing a slight excess of Cu(NO3)2 × 3H2O a transmetalation reaction occurred affording the related copper(II) complex trans-[CuL2(H2O)2] (2). The structures of the compounds were authenticated by single crystal X-ray diffraction revealing, apart from a change in the isomerism, an alteration in the relative orientation of the chelating carboxylate groups and of the pyridine moieties. H-bond interactions stabilize both geometries and expand them into two-dimensional (2D) networks. The transmetalation was confirmed by SEM–EDS analysis. Moreover, the thermodynamic feasibility of the transmetalation is demonstrated by density-functional theory (DFT) studies. The catalytic activities of 1 and 2 for the oxidation of styrene and for the nitroaldol (Henry) C-C coupling reaction were investigated. The copper(II) compound 2 acts as heterogeneous catalyst for the microwave-assisted oxidation of styrene with aqueous hydrogen peroxide, yielding selectively (>99%) benzaldehyde up to 66% of conversion and with a turnover frequency (TOF) of 132 h−1. The zinc(II) complex 1 is the most active catalyst (up to 87% yield) towards the nitroaldol (Henry) coupling reaction between benzaldehyde and nitro-methane or -ethane to afford the corresponding β-nitro alcohols. The reaction of benzaldehyde with nitroethane in the presence of 1 produced 2-nitro-1-phenylpropanol in the syn and the anti diastereoisomeric forms, with a considerable higher selectivity towards the former (66:34).

Versatility of Amide-Functionalized Co(II) and Ni(II) Coordination Polymers: From Thermochromic-Triggered Structural Transformations to Supercapacitors and Electrocatalysts for Water Splitting

“…32,46 It is imperative to mention that a Cd(II)-CP was reported by Luo et al with the same ligand generated in situ from N1,N4-di(pyridin-3-yl)naphthalene-1,4dicarboxamide, 51 and only recently we have reported the synthesis and isolation of this particular ligand along with a mononuclear Zn(II) complex, which undergoes transmetalation upon reaction with a Cu(II) salt. 46 In the IR spectrum of HL (Figure S1), the band at 1703 cm −1 is allocated to the asymmetric stretching vibration of the carbonyl group [ν asym (COO)]. The gradual disappearance of this vibration and concomitant appearance of a vibration centered at 1671 cm −1 (in 1) or at 1674 cm −1 (in 2) indicates coordination of the carboxylate group (Figure S1).…”

“…The pro-ligand HL (Figure ) was prepared by reacting 3-aminopyridine with methyl 4-(chlorocarbonyl)­benzoate and triethylamine in anhydrous THF, followed by hydrolysis according to a known method. , It is imperative to mention that a Cd­(II)-CP was reported by Luo et al with the same ligand generated in situ from N 1, N 4-di­(pyridin-3-yl)­naphthalene-1,4-dicarboxamide, and only recently we have reported the synthesis and isolation of this particular ligand along with a mononuclear Zn­(II) complex, which undergoes transmetalation upon reaction with a Cu­(II) salt . Herein, we have synthesized the new Co­(II)-CP ( 1 ) and Ni­(II)-CP ( 2 ) by mixing a DMF solution of HL and an aqueous solution of CoCl 2 ·6H 2 O and Ni­(NO 3 ) 2 ·6H 2 O, respectively, under hydrothermal conditions (Scheme ).…”

“…The pro-ligand HL was synthesized according to the procedure reported earlier. 46 Synthesis of [Co(L) 2 (H 2 O) 2 ] n (1). HL (10 mg, 0.041 mmol) was dissolved in 1 mL of N,N-dimethylformamide (DMF) by heating, and CoCl 2 •6H 2 O (24 mg, 0.082 mmol) was dissolved independently in 1 mL of water.…”

A binuclear Cu(ii) complex as an efficient photocatalyst for N-alkylation of aromatic amines

“…Due to the ecological and economic benefits, it is desirable to use cheap metal-based catalysts in organic synthesis. In this regard, manganese, 35,36 iron, 37–40 cobalt, 41–43 nickel, 44–46 and Earth-abundant copper 47,48 -based catalysts are also reported for such reactions. This hydrogen auto-transfer methodology is treated as an environmentally friendly process as water is generated as the only by-product.…”

Synthesis of Cu(II) complexes by N,O‐donor ligand transformation and their catalytic role in visible‐light‐driven alcohol oxidation

“…[ 16–21 ] Among various catalytic activities, aerobic oxidation of primary alcohol is an important subclass of catalytic reaction in terms of biological as well as industrial viewpoint. [ 22,23 ] In biological systems, oxidation of alcohols gets catalyzed by various enzymes like alcohol dehydrogenase or galactose oxidase. Whereas alcohol dehydrogenase contains zinc ion, galactose oxidase is a mononuclear type II copper fungal metalloenzyme.…”