Coordination Polymers of 2,5-Dihydroxybenzoquinone and Chloranilic Acid with the (10,3)-a Topology

Crystalline compounds of general composition (NBu4)2[MII2(dhbq)3] (where M = Mn, Fe, Co, Ni, Zn, and Cd and dhbq2– is the dianion of 2,5-dihydroxybenzoquinone) are obtained by reaction of the divalent metal acetate (or the sulfate in the case of Fe) with 2,5-diaminobenzoquinone and an excess of NBu4Br in aqueous solution at 115 °C in sealed tubes. The dhbq2– ligand is generated in situ by hydrolysis of the 2,5-diaminobenzoquinone. We have been unable to obtain these compounds in a crystalline form suitable for single crystal X-ray diffraction studies directly from H2dhbq itself. A structural feature common to this series is the presence of two interpenetrating [MII2(dhbq)3]2– coordination networks, each with the chiral (10,3)-a topology, with the two independent nets being of opposite hand—unprecedented circumstances for dhbq-based coordination polymers. Crystals of the same zinc compound as that obtained above from 2,5-diaminobenzoquinone can alternatively be obtained by in situ aerial oxidation of 1,2,4,5-tetrahydroxybenzene in the presence of Zn(OAc)2 and NBu4Br in aqueous methanol at room temperature. Analogous in situ aerial oxidation of 1,2,4,5-tetrahydroxy-3,6-dichlorobenzene in the presence of Mn(OAc)2 and NBu4Br affords crystalline samples of the chloranilate (NBu4)2[MnII2(can)3], which contains two interpenetrating (10,3)-a [MnII2(can)3]2– networks of opposite hand.