High Stabilization of Low Valency in a Homoleptic ortho-Hydroxybenzoate-bridged Paddlewheel Diruthenium(II,II) Complex

A paddlewheel-type homoleptic diruthenium(II,II) complex ([Ru2II,II]), [Ru2(o-OHPhCO2)4(THF)2] (o-OH), bridged by ortho-hydroxybenzoate (o-OHPhCO2−) and tetrahydrofuran (THF) coordinated at the axial position (Lax) was isolated. The use of meta- and para-substituted hydroxybenzoate (x-OHPhCO2−; x = m and p) produced the corresponding [Ru2II,III] species neutralized by deprotonation of one of the x-OHPhCO2− ligands. In the o-OH complex, the formation of intramolecular hydrogen bonds between the o-OH group and carboxylate oxygen atom stabilized the [Ru2II,II] species significantly. A paddlewheel-type homoleptic diruthenium(II,II) complex ([Ru2II,II]) bridged by ortho-hydroxybenzoate was isolated. The use of meta- and para-substituted hydroxybenzoate produced the corresponding [Ru2II,III] species neutralized by deprotonation of one of the hydroxybenzoate ligands. In the compound obtained from ortho-hydroxybenzoate, the formation of intramolecular hydrogen bonds between the ortho OH group and carboxylate oxygen stabilized the [Ru2II,II] species significantly.