Pyrazole complexes containing

Binary pyrazolate complexes containing divalent metals bridged by two pz groups are known for many transition metals. The increasing interest for this class of complexes stems from the expectation that they may provide useful insights in the field of magnetostructural correlations as well as in multimetal centered catalysis. 

The interest for pyrazolate complexes containing the pz group as a mono-dentate ligand arises because of their recognized usefulness in the synthesis of dinuclear and trinuclear heterometallic derivatives. The mononuclear complex... 

Bonati has classified the pyrazole complexes into two groups compounds containing neutral pyrazoles (HPz), called 2-monohaptopyrazoles since it is the N-2 pyridinic nitrogen lone pair which confers on them the ligand properties and compounds containing pyrazole anions (Pz) which can act as monodentate or, more often, as exobidentate ligands (72CRV497). 

Molybdenum and tungsten hexacarbonyls are able to form anionic complexes (AsPli4)2[(OC)4M( -pz)2M(CO)4] upon reaction with sodium pyrazolate and PluAsCl (72CB3203). The cationic complexes [(rj -Cp)2Mo(/Lt-pz)2Mo(rj -Cp)2] " (n = 2, 3) are known as well (74HCA1988). The other representatives of the complexes containing an exobidentate ligand (26) are derived from 4//-pyrazoles [70ZAAC(379)169]. 

Ovejero, P., Mayoral, M.J., Cano, M. and Lagunas, M.C. (2007) Luminescence of neutral and ionic gold(l) complexes containing pyrazole or pyrazolate-type ligands. Journal of Organometallic Chemistry, 692, 1690-1697. 

The neutral complexes Ni(C3H3N2)2 are obtained by the reaction of hydrated nickel(II) chloride and pyrazole, or imidazole, in an aqueous ammonia solution. These insoluble complexes contain uninegative exobidentate pyrazolates or imidazolates which act as bridges between two metals (104).899,904,905 Two additional ligands such as NH3, H20 or py may be... 

The possibility of formation of an O—O bond at a single Mn site of the OEC, on the other hand, seems remote, but nevertheless, two mononuclear model Mn-peroxo complexes, a peroxo-Mnm porphinato 64 [157] and a peroxo-Mn111 pyrazolylborato complex 65 [158], have been structurally characterized. Both complexes contain side-on peroxo groups. Complex 65 has been crystallized in two forms, one brown and one blue. A peroxo-H—N (pyrazole) hydrogen bond is found only in the blue form (Figure 29). 

Gray and co-workers discovered that, for complexes containing pyrazolate ancillary ligands X, the introduction of methyl substituents into the pyrazole... 

When n = 2 or 3, such structurally characterized ICC, in the majority of cases, have slightly tetrahedrizated c/.v-planar conformations [100]. The effect of the factor examined is so high that even zinc chelates 882 (M = Zn, R = Me, X = S, n — 2) show a considerably planar-distorted structure [209]. An analogous structural situation is observed for cobalt, nickel, and copper complexes containing R — cyclo-(C 12)3, annelated aromatic, and pyrazol fragments [100]. When n increases, for example n = 4 in the complexes capable of tetrahedrizating a structure, the influence of the examined factor decreases. This is observed in the ICC not only with X = S [100,210 212], but also for X = NH 222 [187]. 

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