Density functional theory (DFT) with generalized gradient corrections is used to study the electronic structure of Ni-2(2+). We predict several bound metastable states, all of them having four unpaired electrons. Those states are stabilized against dissociation by a Coulomb barrier. The stability can be explained as due mainly to the interaction between the s electrons of the constituent Ni+ cations, with d(8)s(1) configurations, that pair themselves in a bonding sigma molecular orbital.