Catalytic transesterification reactions of one-dimensional coordination polymers containing paddle-wheel-type units connected by various bridging ligands

Abstract

The paddle-wheel dinuclear unit consists of two CuII ions bridged by four benzoate ligands, and these paddle-wheel [Cu2(O2CPh)4] units are connected by various bridging ligands to form one-dimensional chained compounds formulated as [Cu2(O2CPh)4(μ-L)] (L=2,4-bpe (1), 3,3’3′-dipicam (3), 2,5-Me2pyz (4), pyz (5), 4,4’4′-bpy (6), and 4-pds (7)). The compound 2, formulated as [[Cu2(O2CPh)4][Cu(O2CPh)2](μ-bpp)2], consists of alternating units of [Cu2(O2CPh)4] and [Cu(O2CPh)2] connected by via bpp. Compounds 1–5 and 7 efficiently catalyzed the transesterification of a variety of esters, while it has been reported that Cu-containing complexes or coordination polymers do not usually show catalytic activities for the transesterification reactions. Among these compounds, 2 was most effective. It has been proposed that in the transesterification reaction, a mononuclear type of Cu complex might be the major species of compound 2 in solution, while for all other compounds, a paddle-wheel unit might be the major reactive species.