N e w dinucleating ligands containing pyrazole as an endogenous bridging group, 3,5-bis-[N-(2-pyridylmethyl)carbamoyl] pyrazole ( H3L1), 3,5-bis{N-[2-(diethylamino)ethyl]carbamoyl}pyrazole ( H3L2), and 3,5-bis{N-[3-(dimethylamino)propyl]carbamoyl}pyrazole ( H3L3), and their binuclear copper(i1) complexes with azide or acetate ion as an exogenous bridge, [Cu,L(N,) (H,O),]-H,O (L = L1--L3) and [Cu,L1 (02CMe)]-2MeOH, have been obtained. Cryomagnetic investigations (5-300 K) reveal a significant antiferromagnetic spin exchange for the azide-bridged complexes ( -J = 371-297 cm-'), but a ferromagnetic spin exchange (J > +8.9 cm-l) for the acetate-bridged complex. The azide-bridged complexes are e.s.r. silent. The acetate-bridged complex is unstable in dimethylformamide (dmf) but a quickly prepared dmf frozen solution of the sample givesX-band signals characteristic of a spin-triplet ( S = 1 ) state, together with signals due to a spin doublet (S = $) attributable to monomeric copper(i1). Signals at 81 2, 1 292, and 4 380 G show a seven-line hyperfine structure (Azz = 0.01 03 cm-'); the first and third signals are assigned t o AMs = 1 transitions and the second to the AMs = 2 transition of the parallel resonance of the spintriplet state. E.s.r. simulation based on the spin Hamiltonian for the spin triplet of a dicopper(ii) system gives g , , = 2.533, D = 0.21 0 cm-l, and E = 0.020 cm-l. Only t w o components of the perpendicular resonances are recognizable at 2 11 3 and 3 81 2 G which give g, = 2.055.

ChemInform Abstract The title complexes (Ia) are prepared by known methods. (Ib)-(Id) are obtained in the reaction of the Schiff base in MeOH with Co acetate in the presence of NaOH and Py under reflux, followed by addition of KPF6 in water. (Ib) crystallizes in the space group P1 with Z=2, (Ic) in P21/n with Z=4. The ethylene conformation is gauche for both complexes. The Co(III)/Co(II) reduction potentials of the complexes are not affected by mono-substitution on the ethylene carbon but change on disubstitution. The conformations and electrochemical properties of the complexes are discussed in terms of the steric interaction between the substituents R1 and R2 and the Py molecule coordinated at the apical site (no yields given).

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267ChemInform Abstract The complexes (I) and (II) are obtained from the new dinucleating ligands containing pyrazole as an endogenous bridging group and two chelating arms attached to the 3 and 5 positions of the pyrazole. Cryomagnetic investigations (5-300 K) reveal a significant antiferromagnetic spin exchange for the azide-bridged complexes (I), but a ferromagnetic spin exchange for the acetate-bridged complex (II).

The title complexes (Ia) are prepared by known methods.