Axial binding of 2-methylimidazole to the tetraarylcarboxylatodiruthenium (II, III) core: X-ray crystal structure of [Ru-2(O₂CC₆H₄-p-OMe)(4)(2-mimH)(2)](ClO₄).1.75CH₂Cl₂.H₂O

Abstract

Diruthenium (II. III) complexes of the type [Ru-2(O₂CAr)(4) (2-mimH)(2)](ClO₄) (Ar = C₆H₄-p-X : X=OMe,1, X=Me, 2, 2-mimH=2-methylimidazole) have been isolated from the reaction of Ru₂Cl(O₂CAr)(4) with 2-mimH in CH₂Cl₂ followed by the addition of NaClO₄. The crystal structure of 1.1.75CH₂Cl₂.H₂O has been determined. The crystal belongs to the monoclinic space group p2₁/c with the following unit cell dimensions for the C₄₀H₄₀N₄O₁₆ClRu2.1.75CH₂Cl₂.H₂O (M = 1237.0) : a = 12.347(3)Å, b = 17.615(5)Å, c = 26.148(2)Å, β= 92.88(1)°. v = 5679(2)Å(3). Z=4, D-c = 1.45 g cm(−3). λ(Mo-K-α) = 0.7107 Å, ν(Mo-K-α) = 8.1 cm(−1), T = 293 K, R = 0.0815 (wR(2) = 0.2118) for 5834 reflections with 1 > 2σ(I). The complex has a tetracarboxylatodiruthenium (II, III) core and two axially bound 2-methylimidazole ligands. The Ru-Ru bond length is 2.290(1)Å. The Ru-Ru bond order is 2.5 and the complex is three-electron paramagnetic. The complex shows an irreversible Ru-2(II,III)→Ru-2(Il,II) reduction near −0.2 V vs SCE in CH₂Cl₂-0. 1 MTBAP. The complexes exemplify the first adduct of the tetracarboxylatodiruthenium (II,III) core having N-donor ligands.