Paramagnetic Precursors for Supramolecular Assemblies: Selective Syntheses, Crystal Structures, and Electrochemical and Magnetic Properties of Ru2(O2CMe)4-n(formamidinate)nCl Complexes, n = 1−4
journal contributionposted on 27.12.2004, 00:00 by Panagiotis Angaridis, F. Albert Cotton, Carlos A. Murillo, Dino Villagrán, Xiaoping Wang
Reactions of Ru2(O2CMe)4Cl with two formamidines, HDXyl2,6F = N,N‘-di(2,6-xylyl)formamidine and HDAniF = N,N‘-di(p-anisyl)formamidine, have been investigated with the idea of synthesizing compounds with a mixed set of ligands having different labilities to be used as precursors of paramagnetic, higher-order assemblies. Depending on the formamidine and the reaction conditions, several Ru25+ compounds of the type Ru2(O2CMe)4-n(DArF)nCl (DArF = anion of an N,N‘-diarylformamidine) have been isolated. With the bulky formamidine HXyl2,6F, the compounds Ru2(O2CMe)3(DXyl2,6F)Cl (1) and trans-Ru2(O2CMe)2(DXyl2,6F)2Cl (2) were obtained. From reactions with appropriate amounts of HDAniF in THF and in the presence of NEt3 and LiCl, complexes of the general type Ru2(O2CMe)4-n(DArF)nCl (n = 1−4) were selectively obtained. For n = 2, only the cis isomer was obtained. The choice of solvent in reactions of Ru2(O2CMe)4Cl and HDAniF is of great importance. Toluene favored the formation of the fully substituted Ru25+ complex Ru2(DAniF)4Cl (3), whereas MeOH resulted in a disproportionation reaction that gave the edge-sharing bioctahedral Ru3+Ru3+ complex [trans-Ru2(μ-OMe)2(μ-O2CMe)2(HDAniF)4]Cl2 (6) and the Ru24+ complex Ru2(DAniF)4 (7). Complexes 6 and 7 with an Ru26+ and Ru24+ core, respectively, are diamagnetic, whereas all Ru25+ complexes are paramagnetic with σ2π4δ2(π*δ*)3 ground-state electronic configurations and large zero-field splitting contributions. All compounds show rich and complex electrochemical behavior.