Bis(toluene)chromium fulleride Cr(C7H8)(2) C-60 has been synthesized as a microcrystalline powder from C-60 and Cr(C7H8)(2) in toluene. One electron is transferred from the chromium complex to the fullerene resulting in a magnetic moment of about 2.5 +/-0.2 mu (B) at room temperature, which corresponds to two electron spins per formula unit. At 250 K a reversible phase transition from a primitive cubic high temperature paramagnetic phase to a triclinic low temperature dimer phase occurs. The high temperature phase (Pm (3) over barm, a=9.986 Angstrom) is constituted of dynamically disordered fulleride anions and bis(toluene)chromium (I) cations in a CsCl-type arrangement. The low temperature modification is triclinic (P (1) over bar, a=13.541 Angstrom, b=13.864 Angstrom, c=14.122 Angstrom, alpha =120.59, beta =91.78, gamma =116.88) and carries one unpaired electron per formula unit (mu =1.72 +/-0.01 mu (B)), which according to ESR measurements is localized at the chromium site (g(iso)=1.9870). The phase transition has been monitored by x-ray diffraction, ESR and solid state NMR spectroscopy as well as by SQUID measurements. All experimental results can consistently be described within the scenario of dimer formation of the C-60 monoanions during the transformation.