Heterometallic coordination polymers: syntheses, structures and heterogeneous catalytic applications†
Abstract
A metalloligand Na[Co(L1)2] (1) of the ligand H2L1 (N2,N6-bis(4,5-dihydrothiazol-2-yl)pyridine-2,6-dicarboxamide) offering appended thiazoline rings has been used for the synthesis of one-dimensional {Co3+–Zn2+} (2), {Co3+–Cd2+} (3) and {Co3+–Hg2+} (4) coordination polymers. 1 offers appended thiazoline rings having both soft sulphur and hard nitrogen donors. The crystal structures of 2 and 3 display the coordination of hard thiazoline-N donors to Zn2+ and Cd2+ ions. Interestingly, 4 illustrates the bonding through both hard thiazoline-N and soft thiazoline-S donors. The three heterometallic coordination polymers have been used as reusable heterogeneous catalysts for the ring-opening reactions of oxiranes and thiiranes; Knoevenagel condensation of benzaldehydes and benzothialdehydes; and cyanation reactions of aldehydes and carbothialdehydes. Our results demonstrate that the relative size and Lewis acidity of secondary metals potentially control the catalytic outcome via preferential interaction with the substrates.