Palladium(II) complexes containing pyrazole-derived ligands of biological interest. Four, five and six coordinate palladium(II) complexes with 5(3)-methylpyrazole-3(5)-carboxamide and 5(3)-methylpyrazole-3(5)-carbohydrazide

Abstract Neutral bis-complexes of palladium(II) with 5(3)- methylpyrazole-3(5)-carboxamide (mpa) and 5(3)- methylpyrazole-3(5)carbohydrazide (mph) of the type PdX 2 ·2L (where L = mpa, mph; X = Cl, Br, I, SCN, NO 3 , ClO 4 ) have been synthesised and spectroscopically characterised. Available physico-chemical data indicate the mpa complexes of Pd(II) to be trans -square planar species with the primary ligand molecule showing monodentate behavior through the pyrazolyl ring nitrogen only. The Pd(II)—thiocyanate complex of mpa is proposed to have a pseudo-square pyramidal geometry attained through bridging anionic component. The complexes PdX 2 ·2mph (X = Cl, NO 3 ) appear to be six-coordinate species at least in the solid state; the corresponding thiocyanato variety has in all probability a five coordinate structure. The species, Pd(ClO 4 ) 2 ·2mph is a usual four coordinate one with non-coordinating perchlorate group. The monochelates, PdX 2 ·mph (X = Br, I), are cis -square planar varieties. The ligand molecule, mph, in all cases is believed to function as (N,N) bidentate ligand in its ‘imidol’ form except in the thiocyanate complex where unusually it exhibits both the monodentate and bidentate functions in the same species.