COPPER(II) COORDINATION CHEMISTRY OF POTENTIALLY OCTADENTATE (N-8) TETRAPYRIDYL AND TETRAPYRAZOLYL-PYRIDAZINE LIGANDS - X-RAY CRYSTAL-STRUCTURES OF [CU-2(PTAPY)BR-4].2DMF AND [CU-2(PTAPY)(NO3)(2)(N-3)(H2O)](NO3)(2).1.2CH(3)OH

The structural, electrochemical, ESR and magnetic properties of a seri es of dinuclear copper(II) complexes of two new polyfunctional pyridaz ine ligands, -tetrakis(pyridine-2-ylmethyl)-aminoethanethiolato pyrida zine (PTAPY), and '-tetrakis(pyrazol-1-ylmethyl)-aminoethanethiolato p yridazine (PTAPZ) are discussed. PTAPY and PTAPZ are potentially octad entate (N-8) ligands and on reaction with copper(II) salts form dinucl ear complexes, [Cu-2(PTAPY)X(4)].yH(2)O (X=NO3, y=1 (I); X=Br, y=2 (II )), [Cu-2(PTAPY>(CH3CN)(2)](ClO4)(4).0.5C(2)H(5)OH (III), [Cu-2(PTAPZ) Cl-4].5H(2)O (V), and a tetranuclear complex -2(PTAPY)(NO3)(2)(N-3)(H2 O)](2)(NO3)(2).1.2CH(3)OH (IV). The single crystal X-ray structures of compounds II and IV have been determined, and in each case the ligand is hexadentate. II ([Cu-2(PTAPY)Br-4].2DMF) crystallized in the tricl inic system, space group P $$($) over bar 1, with a=14.037(3), b=14.94 1(4), c=11.782(6) Angstrom, alpha=103.77(3), beta=106.08(3), gamma=84. 59(2)degrees, V=2305(2)Angstrom(3) and Z=2 (R=0.036 and R(w)=0.032). T wo different five-coordinate (CuN3Br2) geometries exist within the sam e molecule. IV crystallized in the triclinic system, space group P $$( $) over bar 1, with a=14.876(5), b=16.172(4), c=10.068(2) Angstrom, al pha=95.45(2), beta=108.40(2), gamma=64.74(2)degrees and Z=2 (R=0.058 a nd R(w)=0.051). The two copper atoms are quite different with six- (ax ially elongated, distorted tetragonal) and five- (distorted square-pyr amidal) coordinate arrangements, and dimerization through azido nitrog ens results in the formation of a tetranuclear azide bridged molecule. The pyridazine nitrogens remain uncoordinated in all complexes and th ere is no magnetic interaction between the distant copper centers. Cyc lic voltammograms are characterized by the presence of either one 'two -electron' or two 'one-electron' (overlapping) reversible or quasi-rev ersible redox processes, associated with the reduction of the dinuclea r copper(II) species to dinuclear copper(I) species.