Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species Using Chromatographic Resolution and Stereoretentive Synthetic Methods

Abstract

A range of chiral building blocks of the type Δ‐ or Λ‐[Ru(pp)2(CO)2]2+ {pp = bidentate ligands bpy (2,2′‐bipyridine), phen (1,10‐phenanthroline) and Me2bpy (4,4′‐dimethyl‐2,2′‐bipyridine)} have been synthesized, and their enantiomeric purity and absolute configurations determined by CD and NMR studies. Decarbonylation using trimethylamine oxide in the presence of the respective pp ligand at room temperature produced the corresponding tris(bidentate) species [Ru(pp)3]2+ with retention of configuration at the ruthenium(II) centre. A general chromatographic technique for resolution of tris‐homoleptic complexes of the type [Ru(pp)3]2+ was investigated, with the absolute configurations of the resolved complexes confirmed by CD studies, and the X‐ray structural analyses of Δ‐(–)‐[Ru(Me2bpy)3]{(–)‐O,O′‐dibenzoyl‐L‐tartrate} and Λ‐(+)‐[Ru(phen)3]{(+)‐O,O′‐di‐4‐toluoyl‐D‐tartrate}. Resolution is also reported for the analogous species containing three potential bridging ligands, [Ru(bpm)3]2+ and [Ru(HAT)3]2+ (bpm = 2,2′‐bipyrimidine; HAT = 1,4,5,8,9,12‐hexaazatriphenylene). The versatility of the chromatographic procedure was demonstrated by the resolution of a series of bis‐heteroleptic complexes [Ru(pp)2(pp′)]2+ {pp′ = dpq (dipyrido[3,2‐d:2,3′‐f]quinoxaline), dpqc (dipyrido[3,2‐a:2,3‐d]‐6,7,8,9‐tetrahydrophenazine), and dppz {dipyrido[3,2‐a:2,3′‐d]phenazine)}.

Redox Characteristics and Anion Association Behaviour of Stereoisomeric Forms of Mono- and Oligonuclear Metal Complexes Using High Pressure Electrochemistry

“…We have developed chromatographic methods for separation of enantiomers by ion-exchange chromatography, using chiral eluents. [5,7,12] Cation-exchange chromatography of the two separated diastereoisomers of [{Ru(bpy) 2 } 2 (µ-dpa)] 4ϩ (isolated from Bands 1 and 2 of the their chromatographic separation) using an aqueous solution of sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate as the eluent showed that the product from Band 2 separated further into two bands (designated 2A and 2B), therefore unambiguously identifying it as the rac form. The isolated cations from this resolution had equal and opposite CD spectra ( Figure 1).…”

“…[4] HPLC grade acetonitrile (BDH) was used for electrochemical measurements; all other solvents were of reagent grade and used without purification. The ruthenium complexes [Ru(bpy) 2 Cl 2 ] · 2 H 2 O, [29] [Ru(pp) 3 ](PF 6 ) 2 {pp ϭ bpy, phen, or Me 4 bpy (4,4Ј,5,5Ј-tetramethyl-2,2Ј-bipyridine)}, [12] [Ru(phen) 2 -(HAT)](PF 6 ) 2 , [5] [{Ru(phen) 2 } 2 (µ-HAT)](PF 6 ) 4 , [5] [{Ru(phen) 2 } 3 (µ-HAT)](PF 6 ) 6 , [5] and [{Ru(bpy) 2 } 2 (µ-mapy)](PF 6 ) 4 and…”

The dichotomy in the DNA-binding behaviour of ruthenium(II) complexes bearing benzoxazole and benzothiazole groups

“…Substitution at the 4-position gave significant quenching of the emission, while functionalization at the 5-position led to negligible luminescence). Chiral separation into the D and K enantiomers was achieved by SP Sephadex C-25 cation-exchange chromatography using (À)-O,O 0 -dibenzoyl-L-tartrate solution as eluent, with the solubility encouraged with the addition of up to 20% acetone [30,31]. Resolution into two separate bands was achieved after three passes through a 1.6 m column for [Ru(bpy) 2 (4,4 0 -bbob)] 2+ and two passes for [Ru(bpy) 2 (5,5 0 -bbob)] 2+ .…”

“…Elemental analysis found: C: 64. 9 [30,31] The hexafluorophosphate salt was initially converted to the water-soluble chloride salt using Amberlite IRA-400 anion-exchange resin prior to cation-exchange chromatography. [Ru(bpy) 2 (4,4 0 -bbob)]Cl 2 (50 mg) was dissolved in water (ca.…”

“…2.3.6. Separation of the enantiomers of [Ru(bpy) 2 (5,5 0 -bbob)] 2+ [30,31] The two enantiomers were separated as above after an ''effective column length" of 2 m and the two bands (D and K) were collected after 3 m of travel. Recovery of the products was achieved in a similar manner to that previously described.…”