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Chiral Induction at Octahedral Ru(II) via the Disassembly of Diruthenium(II,III) Tetracarboxylates Using a Variety of Chiral Diphosphine Ligands

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posted on 18.02.2016, 17:49 by Brandon R. Groves, D. Ian Arbuckle, Ernest Essoun, Travis L. Lundrigan, Ruiyao Wang, Manuel A. S. Aquino
Achiral [Ru2(μ-O2CR)4­(MeOH)2]­(PF6) (R = CH3 or C6H5) reacts with the chiral diphosphines R,R- and S,S-Chiraphos (two chiral centers on ligand between the coordinating P atoms) and R-Prophos (one chiral center on ligand between the coordinating P atoms) leading to a disassembly of the paddlewheel core and the highly diastereoselective production of Λ-[Ru­(η2-O2CC6H5)­(η2-R,R-Chiraphos)2]­(PF6) (Λ-R,R-III), Δ-[Ru­(η2-O2CC6H5)­(η2-S,S-Chiraphos)2]­(PF6) (Δ-S,S-III) (the R = CH3 complexes of Chiraphos were reported in a earlier communication in this journal), and Λ-[Ru­(η2-O2CCH3)­(η2-R-Prophos)2]­(PF6) (Λ-R,R-VI), respectively, in high yield and purity. Reactions of the same starting material with R,R- and S,S-o-tolyl-Dipamp (chiral centers are the coordinating P-atoms) lead to an inversion in the chirality-at-metal producing Λ-[Ru­(η2-O2CC6H5)­(η2-S,S-o-tolyl-Dipamp)2]­(PF6) (Λ-S,S-IV), Δ-[Ru­(η2-O2CC6H5)­(η2-R,R-o-tolyl-Dipamp)2]­(PF6) (Δ-R,R-IV), Λ-[Ru­(η2-O2CCH3)­(η2-S,S-o-tolyl-Dipamp)2]­(PF6) (Λ-S,S-V), and Δ-[Ru­(η2-O2CCH3)­(η2-R,R-o-tolyl-Dipamp)2]­(PF6) (Δ-R,R-V). X-ray crystallography of all but Λ-S,S-V and Δ-R,R-V and solid-state circular dichroism (CD) show that only the indicated diastereomers are present in the solid-state. Solution CD measurements and 31P NMR also indicate their predominance in solution.