Molecular Squares with Paramagnetic Diruthenium Corners:  Synthetic and Crystallographic Challenges

The reaction of Ru2(μ-O2CMe)4Cl with ∼2.5 equiv of HDAniF (HDAniF = N,N‘-di(p-anisyl)formamidine) in refluxing THF resulted in the synthesis of cis-Ru2(μ-DAniF)2(μ-O2CMe)2Cl (1). This Ru2 5+complex, which has two labile acetate groups occupying two equatorial cisoid positions, was used for the construction of discrete paramagnetic supramolecular arrays. Subsequent reactions of 1 with HO2C−CO2H (oxalic acid) and 1,4-HO2C−C6H4−CO2H (terephthalic acid) followed by recrystallization from 1,2-C2H4Cl2/hexanes solutions containing wet MeCN or 4-Bu t py (4-tert-butylpyridine) gave crystals of [{cis-Ru2(μ-DAniF)2Cl(H2O)}(μ-oxalate)]4·MeCN·2(C6H14)·12(H2O) (2) and [{cis-Ru2(μ-DAniF)2Cl0.646(4-Bu t py)1.354}(μ-terephthlate)]4Cl1.414·17(1,2-C2H4Cl2)·C6H14 (3), respectively. These are the first polygonal supramolecular assemblies consisting of paramagnetic M2 units at each apex, where M2 = Ru2 5+. Compounds 2 and 3 have been structurally characterized, and their electrochemistry and magnetic properties have been studied. These studies have confirmed that oxalate linkers are better than the terephthalate linkers in effecting electronic and magnetic coupling.