Synthesis of Silsesquioxanes with Substituted Triazole Ring Functionalities and Their Coordination Ability

Abstract

A synthesis of a series of mono-T8 and difunctionalized double-decker silsesquioxanes bearing substituted triazole ring(s) has been reported within this work. The catalytic protocol for their formation is based on the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) process. Diverse alkynes were in the scope of our interest—i.e., aryl, hetaryl, alkyl, silyl, or germyl—and the latter was shown to be the first example of terminal germane alkyne which is reactive in the applied process’ conditions. From the pallet of 15 compounds, three of them with pyridine-triazole and thiophenyl-triazole moiety attached to T8 or DDSQ core were verified in terms of their coordinating properties towards selected transition metals, i.e., Pd(II), Pt(II), and Rh(I). The studies resulted in the formation of four SQs based coordination compounds that were obtained in high yields up to 93% and their thorough spectroscopic characterization is presented. To our knowledge, this is the first example of the DDSQ-based molecular complex possessing bidentate pyridine-triazole ligand binding two Pd(II) ions.

Synthesis of Octachloro- and Octaazido-Functionalized T8-Cages and Application to Recyclable Palladium Catalyst

“…The results of the thermogravimetric analysis (TGA) under N 2 reveal a lower T d5 (158 °C, Table S2) for azido-functionalized 4 compared to that of its tetrachloro counterpart, 3 , displaying a high thermal stability ( T d5 = 358 °C, Table S2). Both T d5 values are comparable to those of related DDSQ frameworks bearing four azido ( T d5 = 167 °C) or four chloro ( T d5 = 359 °C) substituents . As expected, the nature of the external substituents have more impact on the thermal stability of the decorated POSS than the structure of the intrinsically robust silsesquioxane nanocage itself.…”

“…Hence, azido-containing POSSs with various inorganic backbones have been previously reported. For example, we and other groups reported double-decker silsesquioxanes (DDSQs) bearing four or two azido end groups on their side chains, respectively. In all cases, the DDSQs were obtained from their chloro counterparts in the presence of sodium azide.…”