Ionic Complexes of Tetra‐ and Nonanuclear Cage Copper(II) Phenylsilsesquioxanes: Synthesis and High Activity in Oxidative Catalysis

Abstract

Herein, we describe an approach to cage metallasilsesquioxanes by self‐assembly with 1,2‐bis(diphenylphosphino)ethane as a key reactant. This approach allowed us to achieve a unique family of complexes that includes anionic tetra‐ and nonanuclear cage copper(II) sodium silsesquioxane and cationic copper(I) 1,2‐bis(diphenylphosphino)ethane components. Additional representatives of this intriguing metallasilsesquioxane family (Cu9Na6 and Cu9Na3Cs3) were obtained through the replacement of the original ethanol‐based reaction medium by DMSO. The fascinating structural peculiarities of all products were established by using XRD and topological studies. Initial tests for the application of the synthesized complexes as catalysts revealed their very high activity in the homogeneous oxidation of alkanes and alcohols to produce alkyl hydroperoxides, ketones, and amides.

Palanquin-Like Cu4Na4 Silsesquioxane Synthesis (via Oxidation of 1,1-bis(Diphenylphosphino)methane), Structure and Catalytic Activity in Alkane or Alcohol Oxidation with Peroxides

“…Dual behavior was detected for the neocuproine-assisted synthesis of Cu(II)-CLMS: in the case of DMF/dioxane reaction/crystallization media, a similar "ligand synergy product" was formed [37], while DMF media favors the isolation of "ligand antagonism" product with the redistribution of copper centers between silsesquioxane and neocuproine ligands [38], as seen in Figure 1. This particular antagonistic behavior was also found in the P-ligand-assisted self-assembly of Cu-CLMSs; this reaction was found to be tuned with two types of product being available for the reaction with 1,2-bis(diphenylphosphino)ethane [39], as seen in Figure 2.…”

“…Ionic complexes with copper ions redistributed between silsesquioxane and 1,2-bis(diphenylphosphino)ethane ligands (Ref. [39]). Left: Compound C with four copper(II) ions in the cage unit.…”

“…Such coordination provokes a deep distortion of the sandwich skeletons of 1, in comparison with similar fragments described in Refs. [39] (as seen in Figure 1) and [45] (as seen in Figure 2, center) (several distances and angles are provided in Table 1). The six-membered Na-dppm (Na-O-P-C-P-O) rings adopt a sofa conformation with the carbon atom out of the mean plane, which passed through the other atoms of the ring by 0.737(6) Å, as seen in Figure 3, A.…”

Heptanuclear Cage CuII‐Silsesquioxanes: Synthesis, Structure and Catalytic Activity

“…Specific representatives of cage metallacomplexes, namely cagelike metallasilsesquioxanes (CLMSs), are being intensely studied as (pre)catalysts for numerous chemical processes of high relevance . Cage metallasilsesquioxanes were found to be active in alkene polymerization, epoxidation or epoxide ring opening, metathesis, hydroformylation, Ullmann–Goldberg condensation and amidation . Recently, significant attention was drawn to the potential of CLMS application in the homogeneous oxidation of C–H compounds with activity confirmed for Fe‐,, Cr‐, Ni‐, and Co‐based compounds.…”

“…This allowed us to isolate products of different nuclearity from two to nine, , , and different molecular topology. Sometimes, molecular topology and core nuclearity is governed by a promotive action of additional organic (P‐ or N‐based) ligands or solvent molecules intentionally introduced into the reaction medium. However, general regularities underlying the self‐assembly processes in this extremely complex system remain elusive, even though the total number of different CLMS structure types are rapidly increasing.…”