The scandium dimer reacts with dinitrogen in solid argon to form the previously characterized planar cyclic Sc(mu-N)(2)Sc molecule, with the N-N bond being completely cleaved. The cyclic Sc(mu-N)(2)Sc molecules dimerize on annealing to form a cubic Sc4N4 cluster with tetrahedral symmetry, which is a fundamental building block for ScN nanoparticles and crystals.