Synthesis and Characterization of the Series of Compounds Ru₂(O₂CMe)<i>_x</i>(admp)₄_-<i>_x</i>Cl (Hadmp = 2-Amino-4,6-dimethylpyridine, <i>x</i> = 3, 2, 1, 0)

The reaction between Ru2(O2CMe)4Cl and Hadmp (Hadmp = 2-amino-4,6-dimethylpyridine) under different conditions has been investigated. By conducting the reaction in a methanol solution at room temperature the product obtained was Ru2(admp)(O2CMe)3Cl (1). In a melt reaction at 65 °C the product isolated is Ru2(admp)2(O2CMe)2Cl (2); at 100 °C it is Ru2(admp)3(O2CMe)Cl (3); and at 140 °C it is Ru2(admp)4Cl (4). The generality of these reactions was confirmed by the deliberate preparation of Ru2(chp)3(O2CMe)Cl (5) and [Ru2(DPhTA)3(O2CMe)(NCMe)2][BF4] (6). The structures of 1, 2, and 3 were determined by X-ray crystallography. The structure of 1 was determined from crystals of 1·3CH2Cl2 (C16H24Cl7N2O6Ru2), triclinic, P1̄ (No. 2), with a = 11.578(3) Å, b = 12.5607(13) Å, c = 20.903(3) Å, α = 99.927(14)°, β = 100.222(9)°, γ = 102.07(2)°, Z = 4; that of 2, from crystals of 2·2.5CH2Cl2 (C21H30Cl7N4O4Ru2), monoclinic, P21/n (No. 14), with a = 13.091(3) Å, b = 19.098(4) Å, c = 13.720(3) Å, β = 105.51(3)°; that of 3, from crystals of 3·Hadmp·C6H6 (C36H46ClN8O2Ru2), monoclinic, P21/n (No. 14), with a = 15.979(2) Å, b = 14.9294(14) Å, c = 17.131(4) Å, β = 109.21(2)°. The magnetic susceptibilities and electrochemistry of the four title compounds were also studied. It was observed that while compounds 1, 2, and 3 display magnetic moments compatible with the presence of three unpaired electrons and all yield stable one-electron oxidation products, 4 shows only one unpaired electron and the product of its one-electron oxidation decays sufficiently rapidly that no return wave is observed.