New multinuclear zinc complexes with N 4 O 2 coordination spheres David A. McMorran * , Peter J. Steel Department of Chemistry, University of Canterbury, P.O. Box 4800, Christchurch, New Zealand Received 6 August 2002; accepted 27 September 2002 Abstract The preparation and characterisation of the new, potentially octadentate, ligand 1,2,4,5-tetrakis(3-(2-pyridyl)pyrazol-1-yl- methyl)benzene (L 2 ) is reported. This and two related ligands, 1,2-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene (L 1 ) and hexakis (3-(2-pyridyl)pyrazol-1-ylmethyl)benzene (L 3 ) were reacted with zinc(II) acetate to give complexes in which pairs of ligand arms chelate to Zn(OAc) units. The X-ray crystal structures of [Zn(L 1 )(OAc)]PF 6 and ½Zn 2 ðL 2 ÞðOAcÞ 2 ðBPh 4 Þ 2 are reported. Ó 2002 Elsevier Science B.V. All rights reserved. 1. Introduction The synthesis of metal complexes with multiple co- ordination domains is an area of significant current in- terest. Such complexes have been prepared as part of studies in such diverse areas as inter-metallic commu- nication [1], bioinorganic enzyme active site modelling [2], and supramolecular approaches to chiral materials [3] and functional devices [4]. In such polymetallic spe- cies it is desirable to have ligands which have been de- signed so as to coordinate the metal ions with control over the inter-metallic distances and relative geometries. The importance of this has recently been shown in a di- ruthenium(II) complex, where different diastereoisomers have been shown to display significantly different phys- icochemical properties [5]. We report here the preparation of zinc acetate com- plexes of a series of ligands which consist of a central benzene core, appended by multiple (3-(2-pyridyl)pyra- zol-1-ylmethyl) arms, which can each chelate to a metal ion. By varying the number, and relative arrangement, of the arms in these ligands, we hope to control the number and relative arrangement of the coordinated metal ions. Two of the ligands, 1,2-bis(3-(2-pyr- idyl)pyrazol-1-ylmethyl)benzene (L 1 ) [6] and hexakis(3- (2-pyridyl)pyrazol-1-ylmethyl)benzene (L 3 ) [7] have been reported previously, while the preparation of 1,2,4,5-tetrakis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene (L 2 ) is reported here for the first time (see Fig. 1). Re- action with ZnðOAcÞ 2 is found to give complexes in which Zn(OAc) units are coordinated by adjacent pairs of ligand arms, resulting in the zinc atoms having a N 4 O 2 coordination sphere. Structurally characterised examples of zinc complexes of this type are quite rare [8], and only one example of a complex containing more than one zinc atom has been reported [9]. 2. Experimental 1,2,4,5-Tetrakis(bromomethyl)benzene [10], 3-(2-pyr- idyl)pyrazole [11], 1,2-bis(3-(2-pyridyl)pyrazol-1-ylm- ethyl)benzene (L 1 ) [6] and hexakis(3-(2-pyridyl)pyrazol- 1-ylmethyl)benzene (L 3 ) [7] were prepared by literature procedures. NMR spectra were recorded on Varian 500 or 300 MHz NMR spectrometers. IR spectra were re- corded on a Shimadzu FTIR-8201PC spectrophotome- ter. Elemental analyses were performed by the Campbell Microanalytical Laboratory at the University of Otago. 2.1. Preparation of 1,2,4,5-tetrakis(3-(2-pyridyl)pyrazol- 1-ylmethyl)benzene (L 2 ) 1,2,4,5-Tetrakis(bromomethyl)benzene (1.00 g, 2.22 mmol), 3-(2-pyridyl)pyrazole (1.42 g, 9.78 mmol), ben- zene (15 ml), 40% NaOH (5 ml) and 40% Bu 4 NOH (5 drops) were refluxed for 20 h. Ethyl acetate (50 ml) was then added, the layers were separated and the organic layer was washed with brine (10 ml) and dried (MgSO 4 ). Inorganic Chemistry Communications 6 (2003) 43–47 www.elsevier.com/locate/inoche * Corresponding author. Tel.: +64-3-3642432; fax: +64-3-3642110. E-mailaddress: p.steel@chem.canterbury.ac.nz (D.A. McMorran). 1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S1387-7003(02)00677-9