A novel and reliable method for the synthesis of polybis(p-pyrazolato-N,N ')copper(II), [ C~( p z )~] , (where pz = N2C3H3), is presented. Single crystals of the polymer suitable for X-ray study have been grown under carefully controlled conditions. Crystals of polybis(p-pyrazolato-N,N1)copper(II) are orthorhombic, a = 7.917(1), b = 11.491(2), c = 7.778(1) A, Z = 4, space group lbam. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.029 and R, = 0.038 for 507 reflections with 1 2 3u(1). The crystal structure consists of infinite double-bridged polymeric chains. The Cu atom has a D2 distorted tetrahedral coordination geometry with Cu-N = 1.957(2) A and N-Cu-N Mots clks : structure cristalline, chaine polymCrique de pyrazolato-cuivre(II), Cchange antiferromagnktique.[Traduit par la revue] Introduction As part of our continuing interest in metal pyrazolate complexes and magnetic exchange effects in transition metal coordination polymers we have initiated a comprehensive study of binary transition metal pyrazolate compounds. Earlier studies in this area have been reviewed by Trofimenko (I) and the intractable nature of the polymeric species noted. Our primary interest in these materials stems from the expectation that they will provide examples of infinite-chain polymers with the bridging pyrazolate ligands acting as pathways for strong magnetic exchange between metal centres. By varying the substituents on the pz (pz = pyrazolyl) rings and studying different metal systems it should be possible to examine systematically how electronic and structural factors affect the magnetic and other properties of these materials. We present here a novel method for the synthesis of the [ C u ( p~)~] . polymer and provide evidence that the methods (2) employed in previous attempts to prepare this compound in fact yield a different product. In addition, the new route described provides excellent crystals of the binary copper(I1) pyrazolate polymer enabling us to report the first X-ray crystal structure determination of this type of complex. We also describe electronic and vibrational spectroscopic, variable temperature magnetic susceptibility (4.2 to 299 K), and thermal studies on this novel material.
Experimental
SynthesisCopper metal shot was cleaned by washing first in 12 M HCl, ther! water and finally acetone. A magnetic stir bar, 10.0 g (147 rnmol) of pyrazole and 8.13 g (78.2 rnmol) of cleansed copper shot were placed in a 100 mL round bottom flask fitted with a reflux condenser. The reaction mixture was heated, with stining, to llO°C and air was bubbled into the molten pyrazole via a Pyrex tube lowered through the condenser. A green solid appeared almost immediately. The mixture was allowed to react for 18 h during which time sublimed pyrazole was periodically scraped back into the reaction mixture. The mixture, which had solidified on cooling, was then washed with 4 X 100 mL portions of CH2C12, 100 mL of high boiling petroleum ether and then suction filtered. [ C u (...
The title compound, [Co40(C5H7N2)6], consists of a central O atom coordinated by four Co II atoms which are themselves bridged in a pairwise fashion by six exobidentate 3,5-dimethylpyrazolate ligands. The coordination geometry about each Co n atom is that of a distorted tetrahedron.
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