Anorganometallic charge-transfer complex, (dineopentylbiferrocenium) (F-1-TCNQ)(3), exhibits an "ionic(I)-ionic(II)'' phase transition: a monovalent solid (D(+)A(3)(-)) at room temperature, it becomes divalent (D(2+)A(3)(2-)) at low temperatures. Features of the transition are discussed in comparison with those of the N-I transition.