Low-Temperature Isolation of a Labile Silylated Hydrazinium-yl Radical Cation, [(Me3Si)(2)N-N(H)SiMe3](.+)

The oxidation of silylated hydrazine, (Me3Si)(2)N-N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium-yl radical cation, [(Me3Si)(2)N-N(H)SiMe3](.+), at very low temperatures (decomposition > -40 degrees C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen-centered radical cation along the N-N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)(2)}(4)](-), crystallization and structural characterization in the solid state were achieved. The hydrazinium-yl radical cation has a significantly shortened N-N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N-N bond has a total bond order of 1.5 with a pi-bond order of 0.5. The pi bond can be regarded as a three-pi-electron, two-center bond.