Synthesis and structural characterization of silver(i), copper(i) coordination polymers and a helicate palladium(ii) complex of dipyrrolylmethane-based dipyrazole ligands: the effect of meso substituents on structural formation

Abstract

A new class of multidentate dipyrrolylmethane based ditopic tecton, 1,9-bis(3,5-dimethylpyrazolylmethyl)dipyrrolylmethane, containing diethyl (L₁) or cyclohexylidene (L₂) substituents at the meso carbon atom were readily synthesized in 28–45% yields in two different ways starting from dipyrrolylmethanes. A one dimensional coordination polymer structure ([(L₂)Ag][BF₄])_n was obtained when L₂ was treated with AgBF₄, whereas the analogous reaction between L₁ and AgBF₄ afforded the dicationic binuclear metallacycle complex [(L₁)₂Ag₂][BF₄]₂. In addition, yet another coordination polymeric structure [(L₁)CuI]_n was obtained from the reaction between L₁ and CuI. The analogous reaction of L₁ with [Pd(PhCN)₂Cl₂] afforded the binuclear palladium complex [(L₁)₂Pd₂Cl₄] having a double-stranded helicate structure. The observed structural differences are attributed to the effects of the substituents present at the meso carbon atom of the ligand, in addition to the nature of the metal centre, coordination number and the preferred geometry.