Two Zeolite-Like Three-Dimensional Coordination Polymers

What is it about?

Monoclinic single crystals of Co[(C6H10)(NH3)2][C6H2(COO)4] · 2H2O have been prepared in aqueous solution at 80 °C. Space group C2/c (no. 15), a=1065.92(8), b=1568.97(9), c=1140.88(9) pm, beta=90.101(6)°, V=1.9080(2) nm3, Z=4. Co2+, which is situated on a twofold crystallographic axis, is coordinated in a moderately distorted tetrahedral fashion by four oxygen atoms stemming from the pyromellitate anions (Co-O 197.87(12) and 200.64(12) pm). A three-dimensionally connected coordination polymer is made up by Co2+ and C6H2(COO)4^4- featuring channel-like voids, which accomodate water molecules and (C6H10)(NH3)2^2+ cations compensating for the negative excess charge of the three-dimensional framework. Thermogravimetric analysis in air showed that the dehydrated compound was stable between 198 and 361 °C. Further decomposition yielded CoO. Zn[(C6H12)(NH3)2][C6H2(COO)4]·1/2H2O (2) was prepared analogously to 1 employing 1,6-diaminohexane. Space group P21/n (no. 14), a=1087.78(8), b=1515.18(11), c=1162.21(10) pm, beta= 96.249(7)°, V=1.9042(3) nm3, Z=4. Zn2+ is coordinated tetrahedrally like Co2+ by oxygen atoms of the pyromellitate anions (Zn-O 195.0(4) - 197.8(4)). The connection of Zn2+ with the anions leads similar to 1 to a three-dimensional framework with voids accomodating (C6H12)(NH3)2^2+ -cations and water molecules. 2 was stable anhydrously between approx. 120 and 340 °C, the further decomposition was completed at 700 °C yielding ZnO.

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