Copper Chloride Catalysis: Do μ₄-Oxido Copper Clusters Play a Significant Role?

Abstract

Copper chloride catalysis is a well-established field in organic and inorganic chemistry. However, in most cases a detailed mechanistic understanding of the individual reaction steps and identification of reactive intermediates are still missing. The present study reports the results of spectroscopic and spectrometric measurements that support formation of copper agglomerates during catalytic processes. The composition of CuCl2·2H2O in several coordinating solvents and the influence of basic coreagents such as NaO(t)Bu and K2CO3 on the structure in the solid state as well as in solution were investigated. Several experiments involving crystal structure determination, IR spectroscopy, and ultra-high-resolution cryospray-ionization mass spectrometry were performed. The crystal structures of [CuCl2(H2O)]·0.5(CH3)2CO (1), [Cu2(CH3CN)2Cl4] (2), [Cu3(CH3CN)3Cl6] (3), [Cu3Cl6(THF)4] (4), [Cu(DMSO)2Cl2] (5), (H2N(CH3)2)2[CuCl3] (6), and [Cu4OCl6(THF)(urea)3]·3THF·urea (8) are reported herein. It can be clearly demonstrated that μ4-oxido copper clusters of the formula [Cu4OCl6(solvent)4] are the main product from the reactions of CuCl2·2H2O and basic coreagents. As a final result of these experiments, it can be stated that μ4-oxido copper clusters most likely play an important role in the mechanism of copper chloride-catalyzed reactions.

Trimetallic Cubane-Type Clusters: Transition-Metal Variation as a Probe of the Roots of Hypoelectronic Metallaheteroboranes

“…Another noticeable feature of 6 is the presence of one μ 4 -oxo moiety inside the adamantane core . It is an example of an inverse coordination complex, where nonmetal oxygen is surrounded by four tantalum metals in a tetrahedral fashion. − Inverse coordination compounds have noteworthy applications, such as hydrogen gas storage, precursors for novel materials for catalysis, and radioactive protective agents . The Ta–O bond length is slightly longer as compared to the M–O bond lengths observed in other adamantane-like inorganic compounds. ,, …”

“…As shown in Table , a series of adamantane-like inorganic compounds of various transition metals (such as Cu, − Mg, Pb, Cr, and Mn) are known, and several of them are utilized in industrial catalysis to biomedical activity. Apart from the wide range of applications, their fascinating structural and bonding features make these complexes very important.…”

Cyanamides as π-Hole Donor Components of Structure-Directing (Cyanamide)···Arene Noncovalent Interactions

“…Various [Cu 4 X 6 OL 4 ] (X = Cl, Br) clusters have previously been reported, including those with L = MeOH, amines, nitriles, cyanamides, Me 2 SO, etc . These copper species were conventionally obtained by codissolution of CuX 2 (X = Cl, Br) and CuO, taken in a 3:1 molar ratio in anhydrous MeOH, followed by the addition of either equivalent amount, or an excess of L. Alternatively, these clusters have been prepared by the reaction of CuCl 2 ·2H 2 O (or undried CuBr 2 ) with N-donor ligands such as amines, imines, or pyridines in weakly coordinating solvents. , The addition of bases, for example, K 2 CO 3 or t BuONa, to solutions of CuCl 2 ·2H 2 O in a donor solvent (e.g., acetone, MeCN, MeOH) facilitates the generation of [Cu 4 Cl 6 O­(solvent) 4 ], which could act as a catalytically active form in CuCl 2 -catalyzed organic transformations …”

Deposition of copper from Cu(i) and Cu(ii) precursors onto HOPG surface: Role of surface defects and choice of a precursor

“…Among all the available metals used for practical supported catalysts, copper has a very prominent place, especially for a number of oxidation reactions. 16,17 In order to understand the foundation of chemical vapor deposition on HOPG, copper precursor molecules can be selected to represent different copper oxidation states and geometries of the starting materials. For example, Cu(hfac)VTMS (copper(i) hexafluoroacetylacetonate vinyl trimethylsilane) and Cu(hfac) 2 (copper(ii) hexafluoroacetylacetonate) are common precursors for ALD or CVD methods and are used to produce either coppercontaining nanoparticles or continuous thin films.…”