A Better Synthesis of Biruthenocene and Molecular Structures of [RuIICp(C5H4C5H4)CpRuIVNCC2H5](BF4)(B2F7)CH3NO2, [RuIICp(2,2′-bipyridine)(p-benzoquinone)]BF4 and Related Salts

An interesting dimerization occurred during the oxidation of ruthenocene with an excess of p-benzoquinone containing BF3·Et2O (abbreviated p-Bq/BF3) in a mixed solution of benzene and hexane, which gave biruthenocenium(BF4)2 (A) in 89% yield. Reduction of A with TiCl3 gave biruthenocene in a good yield (68% from ruthenocene), which is the most elegant preparation of biruthenocene. Recrystallization of A from CH3NO2 containing C2H5CN gave a mixed-valence salt 3 formulated as [RuIICp(C5H4C5H4)CpRuIVC2H5CN](BF4)(B2F7)CH3NO2 in which C2H5CN coordinated to the RuIV center. The crystal of 3 was found to be monoclinic, space group P21/a, a = 9.8930(8), b = 15.445(3), c = 19.728(3)Å, β = 92.57(1)°, V = 3011.3(1) Å3, Z = 4, and the final R = 0.075and Rw = 0.093. Recrystallization of A from CH3NO2 containing 2,2′-bipyridine and p-benzoquinone gave a yellow planar salt 4 formulated as [RuIICp(2,2′-bipyridine)(p-benzoquinone)]BF4 in which the olefin moiety of p-benzoquinone coordinated to the RuIV center in η2-form. Salt 4 was also synthesized by the reaction of bromoruthenocenium (BF4) with p-benzoquinone and 2,2′-bipyridine in CH3NO2. The crystal of 4 was found to be monoclinic, space group P21, a = 8.516(3), b = 9.934(4), c = 11.995(4) Å, β = 103.78(1)°, V = 985.6(6) Å3, Z = 2, and the final R = 0.040 and Rw = 0.050. The same p-Bq/BF3 oxidation of osmocene gave an orange red salt 5 formulated as [Cp2OsIVFBF3]BF4 in which one of the F− atom of the BF4− ion coordinated to the OsIV center. The crystal of 5 was found to be monoclinic, space group P21/c, a = 8.065(1), b = 12.048(1), c = 16.730(2) Å, β = 94.497(8)°, V = 1620.6(3) Å3, Z = 4, and the final R = 0.055 and Rw = 0.070.