Synthesis, magnetochemical studies and X-ray molecular structures of some mononuclear copper(II)-1H-pyrazole adducts and mono(mu-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 pre pared and characterized, where HL and L, respectively, refer to the mononeg ative and dinegative N-salicylidenearoylhydrazine anions. The X-ray crystal and molecular structure of [monochloro(N-salicylidenebenzoylhydrazinato)ON O(-1)monopyrazole] copper(II) monohydrate, [Cu(HSBzh)HPz Cl] H2O, and [(N-s alicylidenebenzoythydrazinato)ONO(-2)monopyrazole] copper(II) hemihydrate, [Cu(SBzh)HPz] 1/2H(2)O, were determined. The Cu(II) in [Cu(HSBzh)HPz Cl] H2 O is in a distorted square pyramidal environment and is bound in the equato rial plane with the mononegative tridentate aroylhydrazone anion and pyrazo le nitrogen, the axial fifth coordination site is occupied by a chloride io n. On the other hand, the complex [Cu(SBzh)HPz] 1/2H(2)O consists of two mo nomeric crystallographically independent but chemically similar molecules. In each molecule. the Cu(II) is in a distorted square planar geometry and i s coordinated to the dinegative tridentate aroylhydrazone via the phenoxy o xygen, azomethine nitrogen and enolimide oxygen, and the fourth coordinatio n site is occupied by the pyrazole nitrogen. The mono(mu -pyrazolate) dicop per(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 det ermined. In this complex, two copper(II) atoms are bridged by only one pyra zolate anion forming a dicopper mono(mu -pyrazolate) unit. Each two units a re 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 behaviou r with -2J values varying from 25 to 36 cm(-1) (C) 2001 Elsevier Science Lt d. All rights reserved.