Diorganotin(IV) derivatives containing the 3,5-dimethyl-4-(4′- pyridyl)pyrazole ligand

Article abstract of DOI:10.1016/j.poly.2004.11.016

3,5-Dimethyl-4-(4′-pyridyl)pyrazole, prepared by the reaction of 3-(4-pyridyl)pentane-2,4-dione with hydrazine hydrate, reacts with R ₂SnCl₂ (R = Ph, Et and n-Bu) in a 1:1 ratio to yield 2:1 (ligand:tin) adducts. In the crystal structure of the Ph₂SnCl ₂ adduct, two 3,5-dimethyl-4-(4′-pyridyl)pyrazole ligands coordinate to the tin atom through the pyridyl nitrogen atom instead of the pyrazolyl nitrogen atom, and the molecules are connected into a linear chain through intermolecular N-H?N hydrogen bonds. The reaction of 3,5-dimethyl-4-(4′-pyridyl)pyrazole with dibromomethane under phase transfer catalytic conditions affords bis[3,5-dimethyl-4-(4′-pyridyl) pyrazol-1-yl]methane. Treatment of this potential polydentate ligand with R ₂SnCl₂ yields 1:1 adducts, in which bis[3,5-dimethyl-4- (4′-pyridyl)pyrazol-1-yl]methane coordinates to the tin atom through the pyridyl nitrogen atom to form six-coordinate diorganotin linkage coordination polymers, leading to a bridging instead of a general chelating metal coordination. In all new complexes, the pyridyl nitrogen atom exhibits stronger donating ability than the pyrazolyl nitrogen to the tin atom.