A systematic method for the incorporation of the {(eta(6)-MenC6H6-n)Fe} fragment into the dicarbollide cage was developed based on reactions between [(eta(6)-MenC6H6-n,)(2)Fe][PF6](2) salts (1) and Tl-2[nido-7,8-C2B9H11]. These reactions proceed with elimination of one arene ligand to generate a complete series of the neutral [1-(eta(6)-MenC6H6-n)-closo-1,2,3-FeC2B9H11] (2) complexes with n=1-6 in yields ranging 15 70% depending on the arene. The structures of mesitylene and pentamethylbenzene complexes were established by X-ray diffraction analyses. All compounds were characterized by B-11 and H-1 NMR measurements, mass spectra, melting points and elemental analyses. Correlations between selected and B-11 NMR parameters and the Fe-II/III redox potentials and the number of arene methyls for complexes 2 are linear. These facts establish direct evidence for a strictly additive character of electron donation by the methyl substituents to the arene ring and further to the Fe center and the second (dicarbollide) ligand. Correlations between the number of arene methyls (n) and selected H-1 and B-11 NMR parameters or the Fe-II/III redox potentials for complexes [1-(eta(6)-MenC(6)H(6-n))-closo-1,2,3-FeC2B9H11] are of strictly linear character.