Molecular structure of alpha,alpha-carbonium [1.1]ferrocenylruthenocenophane plus BF4- salt

The oxidation of [1.1]ferrocenylruthenocenophane (1) with bromo- or chlororuthenocenium (BF4-)-B-+ ([RcHX](BF4-)-B-+; X=Br, Cl) was carried out giving a diamagnetic salt 2. The crystal form of 2 is monoclinic, space group P2(1)/n, a=10.556(3), b=13.634(3), c=13.795(2) Angstrom, beta=107.27(2)degrees, V=1896.0(8) Angstrom(3), Z=4, and the final R=0.045 and R(w)=0.040, based on the results of the single-crystal X-ray diffraction study. The distance between the Ru and Fe is ca. 4.495(2) Angstrom, which is much shorter than 1 (4.792(2) Angstrom). The structure of the cation is illustrated as a resonance hybrid canonical structure of alpha,alpha-carbonium-type expressed as [Fe-II(C5H4CH2C5H4)(C5H4CHC5H4)Ru](+) and eta(6)-fulvalne-type as [Fe-II(C5H4CH2C5H4)(C5H4CH=C5H4)Ru](+). The two C5H4 rings on the Ru side are tilted greatly (the dihedral angle of the rings is 10.92 degrees) owing to the Ru-C-alpha(+) bond formation (2.407(6) Angstrom), which gives the stability of the carbonium center -CH+-. Fe-57 Mossbauer, H-1, C-13 and C-13 CP/MAS NMR spectroscopic studies support the above formula.