Ligands containing multiple binding sites are of interest for the construction of structural and reactivity models of certain metallobiomolecules as well as polyelectronic systems."' The ligand 3,6-bis(T-pyridyI)pyridazine (dppn)Iz1 complexes a variety of metal ions, [3] and given our interest in dicopper-containing proteins, the binuclear copper(I1) complexes of dppn attracted our attention.I4I Therefore, we studied the interaction of copper(1) ions with this ligand and report here the structure and some properties of the resultant complexes. Scheme 1 Structure of the dppn hgand. The numbering is based on the interpretation of its NMR spectra.When 2 equivalents of dppn were added to 1 equivalent of [Cu(CF,SO,)], . C6H6['] in benzene, a brown precipitate was isolated (85 % yield) and recrystallized as brown crystals from acetone and ether. Microanalytical results combined with the FAB+ mass spectrum (FAB = Fast Atom Bombardment) indicate that the isolated product is the tetrameric complex 1.The 'H and I3C NMR spectra of 1 reveal the molecule to be highly symmetric, with a pattern of resonances similar to that of the free ligand. Additionally, the IR spectrum of 1 indicates that dppn binds in a tetradentate fashion.[4a1 X-ray quality crystals of 1 . 2CH,OH were obtained from a 1 : 1 : 1 mixture of methanol/acetone/ethanol.shows that the complex consists of discrete [ C~, ( d p p n )~]~+ ions and uncoordinated triflate ions with two methanol molecules of crystallization. The structure of the complex cation (Fig. I), which has crystallographically imposed C, symmetry about the Cul -Cu2 diagonal, is best described as a planar arrangement of four copper atoms lying at the vertices of a slightly distorted rhombus, with sides of length 3.566 (1) 131.8(3), N9-Cu3-N27 132.5(2), N9-Cu3-N32 117.5(2), N14-Cu3-N27 119.3(2), 107.2(3). N19-Cul-N26 and N19-Cul-N26 80.212). N19-Cul-N26' and N19-and Nl'-Cu2-N8' 79.9(2), NI-Cu2-N8' and Nl'-Cu2-N8 132.0(2), NS-Cu2-N8' N14-Cu3-N32 131.1(2), N9-Cu3-NI4 El.8(2), N27-Cu3-N32 81.7(2). Bottom: Representation of 1 .2CH,OH using the Chem-Ray program. atoms are spanned by four dppn ligands, two lying above the Cu, mean plane and two below. The distorted tetrahedral environment about each copper(1) ion is provided by two different dppn ligands, each of which supply a pyridine and a pyridazine nitrogen donor atom. Each of the individual
