Ferrocene compounds. XXXVIII. Dimethyl ferrocene-1,1'-dicarboxylate.

In the title compound, [Fe(C(7)H(7)O(2))(2)], the cyclopentadienyl rings and the two attached methoxycarbonyl groups, in an anti arrangement, form an extended pi-conjugated system. The Fe-C distances range from 2.035 (3) to 2.061 (3) A and the average value of the C-C bond lengths in the two cyclopentadienyl rings is 1.419 (5) A. The rings are almost parallel to one another [1.0 (2) degrees ] and are mutually twisted from an eclipsed conformation by only 1.8 (3) degrees (average value). The methoxycarbonyl groups are twisted out of the plane of the cyclopentadienyl rings by 6.5 (4) and 15.7 (4) degrees, respectively. The molecules are joined into dimers by intermolecular C-H.O hydrogen bonds that form ten-membered rings. The same types of hydrogen bonds form eight-membered rings and infinite chains along the b axis.