Synthesis and Structural Properties of the Binary Framework C-N Compounds of Be, Mg, Al, and Tl

摘要

The synthesis of crystalline Be(CN)_2 and Mg(CN)_2 has been demonstrated and X-ray diffraction studies indicate simple-cubic structures with four-coordinate metal atoms surrounded by an average of two N and two C atoms. The symmetry of Be(CN)_2 is Pn3m, a = 5.339(1)A, Z = 2. The symmetry of Mg(CN)_2 is also Pn3m, a = 6.122(1)A, Z = 2. A thallium cyanide with composition Tl(CN)_2 was prepared and was shown to have a similar simple-cubic structure with a = 6.660(1)A. On the basis of the X-ray diffraction pattern, IR spectra, and combustion analysis, this material is assigned the formula Tl~ITl~(III)(CN)_4. Crystalline Al(CN)_3 with simple-cubic structure has been prepared for the first time. Rietveld refinement indicated that the structure incorporates CN groups with orientational disorder in a Prussian-blue-like octahedral network. ~27Al NMR spectroscopy confirmed C,N disorder in cubic Al(CN)_3. The symmetry for Al(CN)_3 is Pm3m, a = 5.205(1)A.