Coordination studies of copper(II), cobalt(II) and iron(II) with isomeric pyridyl–tetrazole ligands

Abstract

The reaction of 2-(2H-tetrazol-5-yl)pyridine (L1) with 1,6-dibromohexane results in formation of the isomers 2-(6′′-bromohexyl-(1-tetrazol-5-yl)pyridine (L2) and 2-(6′′-bromohexyl-(2-tetrazol-5-yl)pyridine (L3 compounds. X-ray crystal structures were obtained for complexes 1-5. In each complex, ligands L2 and L3 coordinate to the metal centre through the pyridyl N atom and the 1-N site of the tetrazole ring, and the pyridyl-tetrazole ligand remains planar in all cases except 3. Complexes 1 and 2 comprise a central Cu 2 Cl 2 dimeric core with Cu(II) in an essentially square-pyramidal coordination environment. Complexes 3 and 4 contain Co(II) in a distorted octahedral coordination environment.In 3, the pyridyl and tetrazole rings of L2 are twisted with respect to each other and the complex adopts a puckered conformation in its equatorial plane. Complex 5 contains water molecules coordinated to Fe(II) in the axial sites, which form hydrogen bonds to the perchlorate counter anions.3

Coordination studies of copper(II), nickel(II), cobalt(II) and zinc(II) salts with pyridyl–tetrazole ligands containing alkyl or alkyl halide pendant arms

“…Each pyridyl-tetrazole ligand binds to the cobalt(II) ion through one tetrazole nitrogen atom at the 1-N site and through the pyridyl nitrogen atom. As previously observed [10], the pyridine rings are not coplanar with the tetrazole rings and so both complexes display a slightly puckered conformation. The planes between the pyridine and tetrazole rings form interplanar angles of 3.8(5)°a nd 1.6(5)°in Co(L5A) 2 (NCS) 2 and 4.5(4) The compound 2-(2H-tetrazol-5-yl)pyridine (L1), the bromohexyl derivatives 2-(6 00 -bromoalkyl-(1-tetrazol-5-yl)pyridine (L2C) and 2-(6 00 -bromoalkyl-(2-tetrazol-5-yl)pyridine (L3C) as well as the copper complexes [Cu(L2C)Cl 2 ] 2 and [Cu(L3C)Cl 2 ] 2 have been reported previously [10].…”

“…The reaction of 2-(2H-tetrazol-5-yl)pyridine (L1) with either the appropriate 1,n-dibromoalkanes (n = 3, 4, 6 or 8) or bromoalkane in acetonitrile with potassium carbonate as base resulted in the formation of either 2-(n 00 -bromoalkyl-(1-tetrazol-5-yl)pyridine (L2A-D) and 2-(n 00 -bromoalkyl- (2-tetrazol-5-yl)pyridine (L3A-D) or 2-(alkyl-(1-tetrazol-5-yl)pyridine (L4A-C) and 2-(alkyl- (2-tetrazol-5-yl)pyridine (L5A-C), arising from alkylation at either the 1-N or 2-N positions, in a manner similar to that described in the literature [10], as shown in Scheme 1. Column chromatography was used to separate the isomeric products.…”

“…In this follow-on paper from the X-ray crystallographic study of 2-(2H-tetrazol-5-yl)pyridine derivatives containing a 6-bromohexyl pendant arm [10], 2-(2H-tetrazol-5-yl)pyridine derivatives containing either an n-bromoalkyl pendant arm (n = 3, 4, 6, 8) or an n-alkyl chain (R = butyl, hexyl or octyl) at either the 1-N or 2-N position of the tetrazole ring were synthesised. Their complexation reactions with several M(II) chloride complexes (M = Cu, Ni, Zn) and also Co(NCS) 2 were studied.…”

“…To expand this area, we are currently investigating the use of tetrazole-containing compounds as potential metal-based therapeutic agents, especially as anti-cancer or anti-fungicidal agents. Recently, we have described the synthesis of some pyridyl-tetrazole compounds containing bromohexyl pendant arms and examined their coordination chemistry with Fe(II), Co(II) and Cu(II) salts, a range of metal cations which the human body can tolerate [10]. As part of our current investigations into the coordination chemistry of pyridyl-tetrazole derivatives, we have altered the pendant arm extending from the tetrazole ring to include other alkyl bromide chains as well as alkyl chain on their own (see Scheme 1).…”

Tetrazolium Compounds: Synthesis and Applications in Medicine

“…was conducted in MeOH (0.5 M) in the presence of a catalytic amount of HCl (2 mol %, 1.0 M in Et 2 O solution) at 60 °C [ 13 , 14 ]. One of the main procedures frequently used for the preparation of 5-substituted tetrazoles 7 involves heating a suspension of 6 , sodium azide, ammonium chloride and lithium chloride (1.20 g, 28 mmol) in anhydrous dimethylformamide (DMF) under stirring at 110 °C [ 15 , 16 , 17 ]. Compound 7 was also obtained in a sealed pressure vessel reaction where NaN 3 dissolved in H 2 O, compound 6 , ammonium chloride, ammonium fluoride and propane-1,2-diol (DPOL) were stirred and heated for 48 h [ 18 ].…”