Chiral Ruthenium Complexes with P,N-Ligands Derived from (S)-Proline

Abstract

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-(∆)-stereoisomer (∆-3) in THF and as the (Λ)-stereoisomer (Λ-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 ∆-3 in boiling dioxane affords (∆)-and (Λ)-stereoisomers of the carbene ruthenium complex (7), due to facile dehydrogenation of the N-Me groups of the ligand.

Ruthenium(II) Complexes Bearing Carboxylato and 2‐Oxocarboxylato Ligands

“…In particular, a slight high‐field shift of the acetate 13 C NMR signal (CO 2 − : 187.4 ppm) is indicative of this adduct, 6· H 2 O. The shift is in good agreement with the results recently reported by Alper et al for the formation of [Ru(OAc) 2 (H 2 O)(Ph 2 PProMe) 2 ] 20. An NMR sample of sodium acetate and three equivalents of water in CD 2 Cl 2 shows a 13 C NMR signal at δ = 181.6 ppm.…”

Coordinatively Unsaturated Cationic and Zwitterionic [Cp*Ru(κ2‐P,N)] Complexes: Ligand‐Assisted Double‐Geminal CH Bond Activation and Reversible α‐H Elimination at Ruthenium

“…The identification of 8 b as a hydridocarbene complex was based in part on the observation of 1 H NMR signals at δ =12.1 and −12.4 ppm, as well as a 13 C NMR resonance at δ =244.1 ppm; the structure of 8 b was subsequently confirmed by X‐ray diffraction analysis (Figure 1). 8b,d The contracted RuC27 (1.886(2) Å) and NC27 (1.374(3) Å) distances in 8 b are comparable to some other N‐stabilized RuC fragments 12b–d. These interatomic distances, the short NC2 distance (1.384(3) Å; cf.…”

Synthesis of Ruthenium Hydride Complexes Containing beta-Aminophosphine Ligands Derived from Amino Acids and their use in the H2-Hydrogenation of Ketones and Imines

“…[12] This geometry is maintained in solution as evidenced by the large 2 J P,P coupling of 335 Hz in the 31 P NMR spectrum. The phosphorus nuclei in this complex are non-equivalent because the 5-membered proline rings also take up two different configurations in the same molecule with the N atoms having opposite configurations.…”

“…No enantioselectivity was observed. Kuznetsov and Alper [12] described the synthesis of the complex trans, trans, trans-Ru(OAc) 2 (Ppro) 2 where Ppro is the beta-aminophosphine, 2-(S)-diphenylphosphinopyrrolidine derived from (S)-proline. A tridentate NPN ligand, also derived from (S)-proline, has been described and used for the asymmetric transfer hydrogenation of ketones catalyzed by ruthenium(II).…”