Ruthenium carbonyl complexes with α-substituted oxime derivatives of terpenes as ligands

Abstract

The reactions of Ru₃(CO)₁₂ with oximes of α-substituted caran-4-one, lemonen-5- and pinan-3-one derivatives were studied. The reactions at elevated temperatures yield binu-clear complexes Ru₂(CO)₄L₂, with two ruthenium atoms bridging two terpenoid ligands (L) through the oxime groups and coordinated additionally to a nitrogen or sulfur atom of the NR₂ or SR groups respectively. The reactions carried out at room temperature in the presense of Me₃NO yield trinuclear complexes Ru₃(CO)₈L₂ with analogous coordination of the terpenoid ligands. In a solution at room temperature these clusters readily transform to binuclear complexes. The NMR spectroscopy shows the stereochemical nonrigidity of the complexes with the S-CH₂-Ph fragment: at room temperature in a solution the benzyl radical undergoes slow rotation about the S-C bond and a change of the conformation of carane and pinane carbocycles occurs more rapidly. The reactions with pinane and carane derivatives are stereospecific yielding only one of the possible diastereoisomers. More flexible limonene derivative form both diastereoisomers.