Three charge-transfer complexes (CTC) η^5-C~5H~5Fe[C~5H~4C(CH~3)=N-C~6H~4R-p]- η^5/C~6~0 (2a R=H; 2b R=CH~3; 2c R=OCH~3) were formed in toluene at room temperature through the interaction between C~6~0 and three ferrocenylketimines η^5-C~5H~5Fe[C~5H~4C (CH~3)=N-C~6H~4R-p]-η^5 (1a R=H; 1b R=CH~3; 1c R=OCH~3). The UV spectra of these CTC gave the evidence for their existence. The CTC formation constants of 2a, 2b and 2c at room temperature in toluene were determined to be 0.769mol^-^1·dm^3, 0.928mol^-^1·dm^3 and 2.353mol^-^1·dm^3, respectively using the Benesi-Hildebrand equation. These constants are much higher that those of CTC derived from organic amines and C~6~0, which strongly supports the double charge-transfer interaction of C~6~0 with both the ferrocenyl and the imine moieties in ferrocenylketimine.

Key words: EQUILIBRIUM CONSTANT, CHARGE TRANSFER, FERROCENE P, FULLERENES