Synthesis, magnetochemical studies and X-ray molecular structures of some mononuclear copper(II)-1H-pyrazole adducts and mono(μ-pyrazolate) bridged dicopper(II) complexes derived from N-salicylidenearoylhydrazines

1H-Pyrazole complexes. [Cu(HL)HPz Cl] nH(2)O and [Cu(L)HPz] nH(2)O were prepared and characterized, where HL and L, respectively, refer to the mononegative and dinegative N-salicylidenearoylhydrazine anions. The X-ray crystal and molecular structure of [monochloro(N-salicylidenebenzoylhydrazinato)ONO(-1)monopyrazole] copper(II) monohydrate, [Cu(HSBzh)HPz Cl] H2O, and [(N-salicylidenebenzoythydrazinato)ONO(-2)monopyrazole] copper(II) hemihydrate, [Cu(SBzh)HPz] 1/2H(2)O, were determined. The Cu(II) in [Cu(HSBzh)HPz Cl] H2O is in a distorted square pyramidal environment and is bound in the equatorial plane with the mononegative tridentate aroylhydrazone anion and pyrazole nitrogen, the axial fifth coordination site is occupied by a chloride ion. On the other hand, the complex [Cu(SBzh)HPz] 1/2H(2)O consists of two monomeric crystallographically independent but chemically similar molecules. In each molecule. the Cu(II) is in a distorted square planar geometry and is coordinated to the dinegative tridentate aroylhydrazone via the phenoxy oxygen, azomethine nitrogen and enolimide oxygen, and the fourth coordination site is occupied by the pyrazole nitrogen. The mono(mu -pyrazolate) dicopper(II) complexes, K[Cu-2(L)(2)Pz] nH(2)O, were also prepared and the X-ray molecular structure of K-2[Cu-4(SBzh)(4)(Pz)(2)] 2H(2)O 1/2CH(3)OH was determined. In this complex, two copper(II) atoms are bridged by only one pyrazolate anion forming a dicopper mono(mu -pyrazolate) unit. Each two units are connected together by a five coordinate K+ cation forming a tetranuclear assembly. These tetranuclear assemblies are connected together by another K+ cation forming a supramolecular structure. Variable temperature magnetic studies on these pyrazolate complexes indicated antiferromagnetic behaviour with -2J values varying from 25 to 36 cm(-1) (C) 2001 Elsevier Science Ltd. All rights reserved.