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17 O effects have been observed on the Mo V EPR signals from sulfite oxidase, xanthine dehydrogenase, and MoO(SC 6 H 5 ) 4 − . The results point to the presence of a rapidly exchangeable oxygen ligand in the molybdenum coordination sphere of the enzymes. Average splittings were on the order of 10 gauss for the enzymes, but only about 2 gauss for MoO(SC 6 H 5 ) 4 − .

Benzimidazolylalcohols, benzimidazolylthiols, and pyrazolylphenols react with MoO 2 (acac) 2 to give octahedral MoO 2 L 2 complexes in the case of the N,O ligands but dimeric Mo 2 O 4 L 2 complexes with the N,S ligands. Heterocycles apparently do not provide enough steric bulk to allow generation of skew- trapezoidal complexes.

Preparation et reactions de CuL 2 BF 4 avec L=emidazoles, pyrazoles et pyridines. Etude RX de Cu(MePz) 2 BF 4 et Cu(Me 3 Py) 2 BF 4

Synthese et caracterisation du coordinat L=bis-[bis-[(pyrazolyl-1)-2 ethyl] aminomethyl]-2,6 p-cresol et etude de son derive complexe dinucleaire Cu(II) μ-hydroxo: C 29 H 38 B 2 Cu 2 F 8 N 10 O 2 cristallise dans P2 1 /c avec Z=4; affinement jusqu'a R=0,073. Mesures de susceptibilite magnetique de 6 a 300 K: fort couplage antiferromagnetique entre les ions cuivre

Several copper(II) complexes have been prepared that use binucleating ligands to yield a coordinatively unsaturated product complex. These complexes will accept an exogenous ligand that binds to a bridging position. We have prepared two families of complexes from 5- or 7-coordinate binucleating ligands that exhibit similar magnetic effects as the exogenous bridging ligands are changed. Complexes of the 7-coordinate binucleating ligand are also especially useful as models of the active site of some binuclear copper proteins (e.g. hemocyanin). We report on our results covering a large series of complexes with exogenous bridging ligands B = Cl - , Br - , OH - , CH 3 CO - 2 , 1,1-N - 3 , 1,3-N - 3 , ClO - 4 , etc. The magnetic exchange interaction for these complexes has not yet been observed to be ferromagnetic, but the magnitude of antiferromagnetic interactions range from Curie-Weiss paramagnetism (B = CH 3 COO - ) to diamagnetism (B = 1,3-N - 3 ).

Synthese de bis{[(pyrazolyl-1)-2 ethyl] methylamino}-2,6 p-cresol et de son derive t-butyl-3 pyrazole. Preparation de complexes Cu(II)-azoture et Cu(I)-carbonyle. Proprietes magnetiques

Preparation et reactions de CuL 2 BF 4 avec L=emidazoles, pyrazoles et pyridines. Etude RX de Cu(MePz) 2 BF 4 et Cu(Me 3 Py) 2 BF 4

Tetraethylammonium borohydride performs the selective reduction of aldehydes under mild conditions.

The first copper(I) dimer having only a single phenolate bridge has been prepared and structurally characterized; its irreversible oxidation suggests the importance of site isolation in type III copper proteins.