Reductive electrocrystallization of [Ru(terpy)(2)](PF6)(2) (where terpy = 2,2':6',2 "-terpyridine) from an acetonitrile solution containing 100 mM TBAPF(6) results in the formation of black crystals. Crystal data: [RU(terpy)2] . (PF6)(2-) [(CH3)(2)CO], monoclinic, space group P2(1)/(c) with a = 20.801(2) Angstrom, b = 8.943(1) Angstrom, c = 19.453(2) Angstrom, beta = 92.524(9)degrees, and Z = 4; [Ru(terpy)(2)] (1), orthorhombic, Fdd2 with a = 39.757(4) Angstrom, b = 56.464(6) Angstrom, c = 8.507(1) Angstrom, and Z = 32. X-ray analysis reveals that the crystals consist exclusively of [Ru(terpy)(2)](degrees) (1), with no solvent or counteranion present in the lattice. [Ru(terpy)(2)]degrees units are structurally very similar to the parent [Ru(terpy)(2)](2+), with nearly perfect octahedral symmetry around the metal center and with two terpy ligands that are basically planar. Analysis of the crystal packing shows that [Ru(terpy)(2)](2+) crystals have close intermolecular distances, while [Ru(terpy)(2)](0) crystals show only intermolecular interactions along the c axis with contacts that are less than 3.5 Angstrom . Analysis of molecular volumes and empty spaces reveals the presence of cavities, which could contain substantial electron density.