Chiral Ruthenium Complexes with P,N-Ligands Derived from (S)-Proline
摘要:
[Ru-2(OAc)(4)] cleanly reacts with 2-(S)-diphenylphosphinomethylpyrrolidine (PPro) and 2-(S)-diphenylphosphinomethyl-N-methylpyrrolidine (PProMe) to give trans, trans, trans-[Ru(OAc)(2)(PPro)(2)] (2) and [Ru(OAc)(2)(PProMe)(2)], respectively, which possess stereogenic nitrogen atoms. The latter complex exists as the cis-P,P-cis-P,N-(Delta)-stereoisomer (Delta -3) in THF and as the (Delta)-stereoisomer (Delta -5) with cis-P,P-trans-N,N coordination geometry in MeOH. Formation of N-based stereocenters occurs selectively, and complexes 2, 3, and 5 are present as single epimers in solution and in the solid state. Thermolysis of Delta -3 in boiling dioxane affords (Delta)- and (Delta)-stereoisomers of the carbene ruthenium complex (7), due to facile dehydrogenation of the N-Me groups of the ligand.