Stable Fe(ii)-based coordination polymers: synthesis, structural diversity and catalytic applications in homo-coupling reactions

Abstract

Herein, we synthesize three new stable Fe(II) coordination polymers, {[Fe₃(tttmb)₄(OH)(NCS)₅]2CH₃OH·H₂O}_n (1), {[Fe₃(tttmb)₄(NCS)₆]·3H₂O}_n (2), and {[Fe₃(tttmb)₂Cl₆(H₂O)₆]·5H₂O}_n (3) (tttmb = 1,3,5-tris(triazole-1-ylmethyl)-2,4,6-trimethyl-benzene) under the regulation of KSCN and solvents and use them as green heterogeneous catalysts in aryl homo-coupling reactions. The catalytic experiments show that 1 and 3 exhibit high efficiency for aryl homo-coupling reactions under an air environment with a yield of up to 80%. Furthermore, the crystal structure analysis reveals that 1 and 3 have coordinated water molecules and OH⁻, which are easily removed from the host materials during the reactions. In contrast, no unsaturated coordination sites are generated in 2 during the reaction process. In addition, the variable temperature magnetic susceptibilities of 1–3 prove that the metal centers of these polymers are bivalent and all of them exhibit a weak antiferromagnetic effect.