Cu42Ge24Na4—A Giant Trimetallic Sesquioxane Cage: Synthesis, Structure, and Catalytic Activity

Alena Kulakova,Alena Kulakova,Xavier Bantreil,Xavier Bantreil,Xavier Bantreil,Xavier Bantreil,Alexey Bilyachenko,Alexey Bilyachenko,Frédéric Lamaty,Frédéric Lamaty,Frédéric Lamaty,Frédéric Lamaty,Elena Shubina,Mikhail Levitsky,Georgiy Shul’Pin,Georgiy Shul’Pin,Pavel Dorovatovskii,Yan Zubavichus,Lidia Shul’Pina,Victor Khrustalev

doi:10.3390/catal8100484

Abstract

Unprecedented germanium-based sesquioxane exhibits an extremely high nuclearity (Cu42Ge24Na4) and unusual encapsulation features. The compound demonstrated a high catalytic activity in the oxidative amidation of alcohols, with cost-effective catalyst loading down to 400 ppm of copper, and in the oxidation of cyclohexane and other alkanes with H2O2 in acetonitrile in the presence of nitric acid. Selectivity parameters and the mode of dependence of initial cyclohexane oxidation rate on initial concentration of the hydrocarbon indicate that the reaction occurs with the participation of hydroxyl radicals and alkyl hydroperoxides are formed as the main primary product. Alcohols have been transformed into the corresponding ketones by the catalytic oxidation with tert-butyl hydroperoxide.

Highlights

The interest to cagelike compounds—which find many unique applications [1,2,3,4]—is determined by the kaleidoscopic multiplicity of their molecular topologies as well as flexibility in the preparation of either metal-free [5,6,7,8] or metal-based [9,10,11,12] complexes
Giving values up to 2200 and 92 h−1. This represents a significant improvement compared to our seminal report on copper-catalyzed oxidative amidation (TON = 44, TOF = 11 h−1 ) [45]
This three-stage method allowed allowed to isolate with an unprecedented high nuclearity (Cu42Ge24Na4) and unusual to isolate product withproduct an unprecedented high nuclearity

Summary

Introduction

The interest to cagelike compounds—which find many unique applications [1,2,3,4]—is determined by the kaleidoscopic multiplicity of their molecular topologies as well as flexibility in the preparation of either metal-free [5,6,7,8] or metal-based [9,10,11,12] complexes (with an opportunity to combine several different metal atoms within one molecule). Heterochained ligands based on (R)Si-O-(R)Si fragments have proven promising for the synthesis of numerous metallacomplexes [4,13,14,15,16]. It is the quantity of organic groups at the silicon atoms that are mainly responsible for the resultant complex’s molecular topology. A high concentration of sodium centers in the resultant sodium germanolate transition metal ions. 3) the enables the of a amount of transition metal ions by a simple and convenient reaction with a transition metal halide. Significant amount of transition metal ions by a simple and convenient reaction with a transition.

General

Central sketch of the cage’s building blockblock

Findings

This three-stage method unique mixed-metal