Diruthenium Compounds Bearing Equatorial Fc-containing Ligands: Synthesis and Electronic Structure

Previously, the synthesis of compounds Ru2(D(3,5-Cl2Ph)F)4−n(O2CFc)nCl (n = 1, 3a; 2, 4a), where D(3,5-Cl2Ph)F is N,N′-di(3,5-dichlorophenyl)formamidinate, from the carboxylate exchange reactions between Ru2(D(3,5-Cl2Ph)F)4−n(OAc)nCl and ferrocene carboxylic acid was communicated. Reported herein is the preparation of analogous compounds Ru2(DmAniF)4−n(O2CFc)nCl (n = 1, 3b; 2, 4b), where DmAniF is N,N′-di(3-methoxyphenyl)formamidinate, from Ru2(DmAniF)4−n(OAc)nCl. Compounds 3 and 4 were characterized with various techniques including X-ray structural determinations of 3a and 4a. Voltammetric behaviors of compounds 3 and 4 were investigated, and stepwise one-electron ferrocene oxidations were observed for both compounds 4a and 4b. Spectral analysis of the monocations [4]+ indicated that they are the Robin−Day class II mixed valent [Fc···Fc]+ species. Measurement and fitting of magnetic data (χT) of 4a between 2 and 300 K revealed a typical zero-field splitting of a S = 3/2 center with D = 77 cm−1, while those of [4a]BF4 are consistent with the presence of S = 3/2 (Ru2) and S = 1/2 (Fc+) centers that are weakly coupled (zJ = −0.76 cm−1).