Combination of a cationic complex [Ni(phen) 3 ] 2 + and an anionic complex [Ni(mnt) 2 ] - has resulted in a novel mixed-valence complex [Ni(phen) 3 ] 2 [Ni(mnt) 2 ] 3 .2DMF (phen=1,10'-phenathroline, mnt=1,2-dicyanovinylene-1,2-dithiolato, DMF=N,N-dimethylformamide). Its crystal structure consists of two different types of [Ni(mnt) 2 ] units: [Ni(mnt) 2 ] - and [Ni(mnt) 2 ] 2 - , the arrangement of the [Ni(mnt) 2 ] anion is found to be quite different from segregated stack layers often found for [Ni(mnt) 2 ]-based compounds. Infrared and electronic spectra also confirmed the existence of both [Ni(mnt) 2 ] - and [Ni(mnt) 2 ] 2 - units.