Revisiting the solution structure of ceric ammonium nitrate.

Ceric ammonium nitrate (CAN) is a single-electron-transfer reagent with unparalleled utility in organic synthesis, and has emerged as a vital feedstock in diverse chemical industries. Most applications use CAN in solution where it is assigned a monomeric [Ce(IV) (NO3 )6 ](2-) structure; an assumption traced to half-century old studies. Using synchrotron X-rays and Raman spectroscopy we challenge this tradition, converging instead on an oxo-bridged dinuclear complex, even in strong nitric acid.