Oxidant-induced intramolecular triazole formation

Abstract

C3-symmetric ligands carrying a rigid triaminoguanidinium backbone are important building blocks for the preparation of supramolecular coordination cages as tetrahedra or trigonal bipyramides. Coordination of Eu(III)- or Gd(III)-ions leads to 1,2,4-triazole formation, which has been reported only rarely. Using Pd(II)-complexes as a model system, this triazole formation could be analyzed in more detail. The preparation of Pd(II)-coordination compounds can be easily done under stoichiometric control. These complexes could be transformed into 1,2,4-triazoles using O2 or H2O2 as an oxidation reagent. The steric demand of the PR3-coligand seems to play a key role in the cyclisation reaction.

Cis‐Dioxo‐molybdenum(VI) Complexes with Diaminoguanidinium and Triaminoguanidinium Schiff Bases and Their Catalytic Application for Epoxidation of Cyclohexene

“…[16][17][18][19][20] For examples, coordination of Pd(II), Eu(III) or Gd (III) with triaminoguanidinium Schiff bases could promote formation of 1,2,4-triazoles. [21] Interactions of ZnCl 2 with triaminoguanidinium Schiff bases led to isolations of Zn3, Zn5, Zn6, and Zn30 complexes due to the different substituents on aryl rings of Schiff bases. [22] Reaction of CdCl 2 and tris-(5-bromo-2-hydroxybenzylidene)-triaminoguanidinium chloride in methanol gave the tightly closed coordination tetrahedra (Et 4 N) 5 (Et 3 NH) 3 [{(CdCl) 3 Br 3 L} 4 ].…”

Triaminoguanidinium-Based Ligands in Supramolecular Chemistry

“…To investigate the triazole formation, model compounds were synthesized [25]. [H 6 Br 3 L]Cl was reacted with Pd(II) salts and phosphine-based co-ligands (PPh 3 , PEt 3 ).…”

A new class of DyIII-SIMs associated with a guanidine-based ligand

“…[28][29][30][31][32][33][34] Surprisingly, such types of ligands have never been used with 4f rare earth metals, except in a single study in which Eu III and Gd III based tetramers were obtained. 35 Unexpectedly, by self-oxidation the inner core configuration of the ligand was totally changed as intra-ligand triazole cyclization was accrued during complexation. For the first time we have succeeded to synthesize a new family of four mononuclear Dy III -SIMs (Scheme 1, Fig.…”