Synthesis of Rare Earth (Oxo)nitridocarbonates by Employment of Supercritical Carbon Dioxide, Single‐source Precursor, Solid‐State, and Ion Exchange Reactions

Novel synthetic approaches to rare earth nitrido‐ and oxonitridocarbonates are described. Dioxy mono‐carbodiimides ( Ln 2 O 2 CN 2 ) from the second half of the lanthanide series are accessible by insertion of supercritical CO 2 into lanthanide amido compounds (e.g. [(Cp 2 ErNH 2 ) 2 ]), forming single‐source precursors. Ammonolyses of amorphous carbamate compounds afford phase pure Ln 2 O 2 CN 2 , which are also accessible via the crystalline carbamate compound [ Ln 2 {μ‐η 1 :η 2 ‐OC(O t Bu)NH}Cp 4 ] ( Ln = Y, Ho, Er, Yb). Urea complexes and homoleptic cyanates of europium and strontium were synthesized by solid‐state reaction of urea with the respective metals. Subsequent thermal treatment (160–240 °C) results in formation of solvent‐free homoleptic cyanates. The Eu 2+ ‐doped compounds [Sr(OCN) 2 (urea)]:Eu 2+ and Sr(OCN) 2 :Eu 2+ as well as the respective pure europium compounds exhibit strong broad band emissions due to 4f 6 5d 1 –4f 7 transitions in the bluish green region. Furthermore, rare earth dicyanamides Ln [N(CN) 2 ] 3 · 2H 2 O as well as Ln [N(CN) 2 ] 3 (with Ln = Eu, Tb, and Gd) were prepared by ion exchange in aqueous solution, followed by evaporation of the solvent at room temperature. Condensed nitridocarbonates such as rare earth tricyanomelaminates [NH 4 ] Ln [HC 6 N 9 ] 2 [H 2 O] 7 · H 2 O ( Ln = La–Nd, Sm–Dy) were obtained through ion exchange reactions. The luminescence properties of the europium and terbium dicyanamides as well as the tricyanomelaminates have been explored in detail.