Structural characterisation of mononuclear zinc(ii) complexes of 4-methyl-3,5-di(2-pyridyl)-4H-1,2,4-triazole with three-atom co-ligands: [ZnII(medpt)2X]ClO4 (X = NCS−, N3 −, NO2 −)

Abstract

The reaction of 4-methyl-3,5-di(2-pyridyl)-4H-1,2,4-triazole (medpt) with Zn(ClO 4 ) 2 Á6H 2 O and NaSCN, NaN 3 or NaNO 2 in a 2:1:1 molar ratio in MeOH/H 2 O (9:1) affords the mononuclear complexes [Zn II (medpt) 2 (NCS)]-ClO 4 , [Zn II (medpt) 2 (N 3 )]ClO 4 and [Zn II (medpt) 2 (NO 2 )]-ClO 4 , respectively. All three complexes have been structurally characterised and found to feature unusual coordination polyhedra for 3,5-di(2-pyridyl)-4H-1,2,4-triazole complexes. In [Zn II (medpt) 2 (NCS)]ClO 4 and [Zn II -(medpt) 2 (N 3 )]ClO 4 , the zinc atom resides within a distorted square-pyramidal N 5 coordination sphere [s = 0.22 and 0.04, respectively] with two bidentate medpt ligands bound equatorially and the pseudohalide ion coordinating as a unidentate co-ligand in the apical position. In contrast, the NO 2 -ion in [Zn II (medpt) 2 (NO 2 )]ClO 4 acts as a bidentate ligand, which leads to a strongly distorted N 4 O 2 coordination environment about the metal centre.

Yellow-Emitting, Pseudo-Octahedral Zinc Complexes of Benzannulated N^N^O Pincer-Type Ligands

“…Many six-coordinate Zn­(II) complexes are also known, particularly when the ligands are not sterically encumbered. Multidentate ligands, in particular, favor the formation of higher coordination numbers, − as do intramolecular interactions (for example, between ligands). Five-coordinate complexes of the form (N^N^N)­ZnCl 2 can be formed using diiminopyridine ligands, while six-coordinate zinc porphyrins have been used to construct three-dimensional coordination polymer networks and in the template-directed synthesis of nano-sized rings .…”