Tetracyanamidometallates with the general formula RbRE[T(CN2)(4)] (RE = La, Pr, Nd, Gd; T = Si, Ge) were prepared by solid state metathesis reactions starting from stoichiometric mixtures of RECl3, A(2)[TF6], and Li-2(CN2). Reactions were studied by differential thermal analysis that showed ignition temperatures between 360 and 390 degrees C for the formation of RbGd[T(CN2)(4)] with T = Si and Ge. The powder diffraction patterns of RbRE[Ge(CN2)(4)] were indexed isotypically to the already known RbRE[Si(CN2)(4)] compound. IR spectra of RbLa[Ge(CN2)(4)] were measured and compared with those of RbLa[Si(CN2)(4)]. Ge-73, Rb-87, and La-139 solid state NMR measurements and density functional theory calculations were used to verify the novel homoleptic [Ge(CN2)(4)](4-) ion. Luminescence properties of Eu3+, Ce3+, and Tb3+ doped samples are reported.