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

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.