The new selenophosphate Rb4P6Se12 features the trans-decalin-like, [P6Se12](4-) anion, a phosphorus-rich species that possesses three parallel P-P bonds and formally p(2+) and P4+ centers. The synthesis of Rb(4)P(6)Sel(2) was accomplished with the reductive addition of P to RbPSe6 and represents an interesting example of how alkali chalcophosphates can serve as starting materials to produce new compounds under mild reaction conditions.