The dianion of 5-cyandminotetrazoline:: C2N62-

Several salts (alkali, Pd(NH3)(3), and (PrNH2)-Pr-i) of 5-cyanoiminotetrazoline (C2N62-, 5-cyanoiminotetrazolinediide, CIT) were investigated. A full characterization by means of X-ray, Raman, NMR techniques, mass spectrometry, and elemental analysis is presented for the (PrNH2)-Pr-i (4), Cs (5), and Pd(NH3)(3) (6) salts. The CIT dianion represents a nitrogen-rich binary CN dianion, and 5 forms monoclinic crystals (a = 7.345(2) angstrom, b = 9.505(2) angstrom, c = 10. 198(2) angstrom, beta = 92.12(3)degrees, space group P2(1)/n, Z = 4). DSC and in situ temperature-dependent X-ray diffraction measurements of the cesium salt 5 revealed an astonishing thermal stability accompanied by a reversible phase transition from the low-temperature alpha modification to the metastable beta modification at 253 degrees C. Above the melting point (334 degrees C), the cesium salt decomposes yielding cesium azide and cesium dicyanamide, which decomposes under further heating under release of nitrogen. The reaction of Cs2CIT with SO2 resulted in the surprising formation of a new cesium salt with the 5-cyaniminotetrazoline-1-sulfonate dianion (Cs2CITSO3 center dot SO2 (7)). 7 crystallizes in the monoclinic space group P2(1) with one SO2 solvent molecule (a = 8.0080(2) angstrom, b = 8.0183(2) angstrom, c = 9.8986(3) angstrom, beta = 108.619(1)degrees, Z = 2). The structure and bonding of the 10 pi dianion are discussed on the basis B3LYP/aug-ccpvTZ computations (MO, NBO), and the three-dimensional array of the cesium salts with respect to the Cs delta+-N delta- in 5 compared to the Cs delta+-N delta- and Cs delta+-O delta- in 7 is discussed. Due to the expected rich bonding modes of the CIT anions, the coordination chemistry with palladium was also studied, yielding monoclinic crystals of [Pd(CIT)(NH3)(3)]center dot H2O (6, a = 7.988(2) angstrom, b = 8.375(2) angstrom, c = 13.541(3) angstrom, beta = 104.560, space group P2(1)/n, Z = 4). In the solid state, the complex is composed of dimers, showing two agostic interactions and an unusual close interplanar pi-pi, stacking of the tetrazole moiety of the CIT ligand.