Ruthenium complexes with 1,1′-biisoquinoline as ligand. Synthesis and hydrogenation activity

The reaction of 1,1′-biisoquinoline (biisoq) with [Ru2(CO)4(CH3COO)2]n gives the binuclear complex [Ru2(biisoq)2(CO)4(CH3COO)](CH3COO). The same reaction in acetic acid gives the mononuclear [Ru(biisoq)3](CH3COO)2 complex instead of the expected [Ru(biisoq)(CO)2(CH3COO)2] compound. Starting from different precursors the following complexes containing the biisoq ligand [Ru(biisoq)3](PF6)2, [Ru2(biisoq)2(Cl)4·NEt3] and [Ru(η6-p-cymene)(Cl)(biisoq)]X [X: Cl, BPh4] were synthesized and characterized. The X-ray structure of [Ru(η6-p-cymene)(Cl)(biisoq)][BPh4] was also determined. Some of these complexes are catalytically active in the homogeneous hydrogenation of alkenes, alkynes and acetone in hydroalcoholic solvents. The better catalytic activity is shown in the hydrogenation of terminal and trans-olefins. Hex-1-ene is hydrogenated at 15 °C, using [Ru(η6-p-cymene)(Cl)(biisoq)]Cl even if a reaction temperature of 40 °C is required to obtain a high yield in 6 h.