Oxidation of 3-(3-or 4-pyridyl)-1,5-diphenylformazans in tetrazolium trichlorometallates: Structural and electrochemical investigation

Abstract

On interacting pyridine-containing formazans with cobalt(II) and copper(II) chlorides the richlorometallates of the corresponding cations are isolated, the structures of which were established by X-ray structural analysis. Using data of cyclic voltamperometry a scheme is proposed for the oxidationreduction process of converting formazans into tetrazolium cations.One of the most vigorously growing directions of supramolecular chemistry is the chemistry of coordination polymers, which are promising materials possessing semiconductor, optical, and magnetic properties [1,2]. The process of forming coordination polymers 2 may consist of the preliminary preparation of a complex ligand 1 (with metal M 1 ) with another metal M 2 . The complex ligands 1 (metalloligands or metalorganic building blocks/tectones) must possess as a minimum, two exodentate groups capable of forming additional coordination bonds [3][4][5][6]. L L L M 1 M 1 M 2 M 2 L L M 1 n 1 2 n N N H N N R 2 R 1 R 3 A R 3 N N N N R 1 R 2 H B Formazans are convenient substrates for building such metalloligands thanks to the presence of potentially chelate chromophoric groupings and the possibility of varying the substituents in positions 1, 3, and 5. It is known that formazans may exist in two forms, chelate A (E,Z) and linear B (E,E) (the Z-form of the azo group is usually not considered) [7]. _______ * Dedicated to deeply respected Academician M. G. Voronkov in connection with his birthday and as a mark of gratitude for his contribution to heterocyclic chemistry __________________________________________________________________________________________ Moscow M. V

Formazans in the synthesis of heterocycles I. Synthesis of azoles (Review)

“…At the meso position of formazan (R 3 ) there can be alkyl, cycloalkyl, aryl, acyl, and heterocyclic substituents, sugar residues, halogens, arylazo, nitrile, ester, dialcoxyphosphoryl, alkyl(aryl)oxy, alkyl(aryl)sulfanyl, amide, and 1,5-diphenylformazyl groups, or a hydrogen atom [1, 2,9,13,22,23,[30][31][32][33]. Macrocyclic formazans containing a spacer between the N-aryl groups are also easily converted into bicyclic tetrazolium salts.…”

“…Practically the whole range of oxidizing agents have been used as oxidizing agents [1,2,4,7,8,13,14,21,30,34,35]. Amyl nitrite has been used from the day of discovery of this reaction up to the present time.…”

“…A very large number of papers, reviews, and books (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and the references therein) and even patent reviews [17] have been devoted to the synthesis of formazans, study of their physical and chemical properties, and identification of practically useful compounds among them, but there has been no separate analysis of the possibilities of using formazans in the synthesis of heterocycles, and this has provided the motivation for writing the present review.…”

Formation and Crystal Structure of 2,3,5-Triphenyltetrazolium Hexachlorophosphate and Dichlorophosphate(V), [TPT]+[PCl6]– and [TPT]+[PO2Cl2]–

“…Otherwise, TTC acts as an excellent chloride ion donor for Lewis acidic metal chlorides as, e. g., SbCl 5 , CdCl 2 , CoCl 2 , or CuCl 2 leading to the respective chlorometallates [2 -5]. With other anions also stable compounds as for example [TPT] + [ReO 4 ] − (triphenyltetrazolium perrhenate), or solvates like TTC · H 2 O (triphenyltetrazolium chloride hydrate), are formed [1,6]. TTC might also be used for studies of salt syntheses where the size of the cationic group is related to the kind and structure of the corresponding anionic units.…”

“…On the other hand, the examples of phosphorus pentachloride acting as chloride ion acceptor resulting in [PCl 6 ] − are scarce. Only CsCl, the strongest Cl 2 ] is known allowing the conclusion that it is built up ionically [19], as well as its homolog [(CH 3 ) 4 As] + [PO 2 Cl 2 ] − [20], referenced in [19]. The first X-ray crystal structure determination of the [PO 2 Cl 2 ] − anion in 2-chloro-1,3-diisopropyl-4,5-dimethyl-imidazolium dichlorophosphate(V) was published 2002 by Kuhn et al [21].…”