Low-Temperature Isolation of a Labile Silylated Hydrazinium-yl Radical Cation, [(Me3 Si)2 N-N(H)SiMe3 ]

Abstract

The oxidation of silylated hydrazine, (Me₃ Si)₂ N-N(H)SiMe₃ , with silver salts led to the formation of a highly labile hydrazinium-yl radical cation, [(Me₃ Si)₂ N-N(H)SiMe₃ ]^.+ , at very low temperatures (decomposition > -40 °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 N₂ Si₃ 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 π-bond order of 0.5. The π bond can be regarded as a three-π-electron, two-center bond.

Keywords: hydrazine; nitrogen; radicals; silylium; synthesis.