Tethered pyrazolyl phosphinate: pyrazolyl-N- and phosphoryl-O-metal coordination in Ph₂P(O){OCH₂CH₂(3,5-Me₂Pz)}

Abstract

Phosphorus pyrazolides, P(O)(3,5-Me₂Pz)₃ or RP(E)(3,5-Me₂Pz)₂ [E = S or O, R = Me or Ph], are hydrolytically sensitive particularly upon interaction with transition metal ions. In this paper, we report a new tethered pyrazolyl phosphinate, Ph₂P(O){OCH₂CH₂(3,5-Me₂Pz)} DPEP (1), where the pyrazolyl group is separated from the phosphorus by means of an ethyleneoxy spacer. 1 has two potential coordination sites in the form of a phosphoryl oxygen atom and a pyrazolyl nitrogen atom. 1 forms hydrolytically stable complexes, (DPEP·CoCl₂)_n (2), (DPEP)₂·CuCl₂ (3), (DPEP·ZnCl₂)_n (4), and (DPEP)₂·PdCl₂ (5). The cobalt(II) and the zinc(II) complexes 2 and 4 show a zigzag polymeric structure in the solid state with a tetrahedral coordination geometry around the metal ion; the ligand DPEP coordinates through its phosphoryl oxygen and the pyrazolyl nitrogen to two neighboring metal ions and functions as a bridging ligand to form the polymeric structure. In contrast to 2 and 4, the copper(II) and the palladium(II) complexes 3 and 5 show a square-planar geometry around the metal ion. Exclusive coordination through the pyrazolyl nitrogens of the ligand 1 is observed. An extensive supramolecular sheetlike two-dimensional polymeric network is observed in the solid-state structures of 3 and 5 as a result of two weak interactions: (a) an intermolecular C-H---O interaction involving the phosphoryl oxygen and an aromatic C-H and (b) a p-p face-to-face stacking interaction between the phenyl groups of two adjacent molecules.