Stereocontrol of Metal-Centred Chirality in Rhodium(III) and Ruthenium(II) Complexes with NN'P Ligand.

Rh(III) and Ru(II) complexes, [RhCl(κ-NN'P-L)][SbF] (1) and [RuCl(κ-NN'P-L)] (2), were synthesised using the tetradentate ligand L (L=N,N-bis[(pyridin-2-yl)methyl]-[2-(diphenylphosphino)phenyl]methanamine). In each case only one diastereomer is detected, featuring cis-disposed pyridine groups. The chloride ligand trans to pyridine can be selectively abstracted by AgSbF, with the ruthenium complex (2) reacting more readily at room temperature compared to the rhodium complex (1) which requires elevated temperatures.

Dynamic Configuration on a Chiral-at-Rhodium Catalyst Featuring a Flexible Tetradentate Ligand.

The unique dynamic configuration of an enantioselective chiral-at-metal catalyst based on Rh(III) and a non-chiral tetradentate ligand is described and resolved. At room temperature, the catalyst undergoes a dynamic configuration process leading to the formation of two interconvertible metal-stereoisomers, remarkably without racemization. Density functional theory (DFT) calculations indicate that this metal-isomerization proceeds via a concerted transition state, which features a trigonal bipyramidal geometry stabilized by the tetradentate ligand.

Synthesis of chiral-at-metal rhodium complexes from achiral tripodal tetradentate ligands: resolution and application to enantioselective Diels-Alder and 1,3-dipolar cycloadditions.

An improved synthesis of the racemic rhodium compound [RhCl(κ ,,',-L1)] (1) containing an achiral tripodal tetradentate ligand is reported. Their derived solvate complexes [Rh(κ ,,',-L1)(Solv)][SbF] (Solv = NCMe, 2; HO, 3) are resolved into their two enantiomers. Complexes 2 and 3 catalyze the Diels-Alder (DA) reaction between methacrolein and cyclopentadiene and the 1,3-dipolar cycloaddition reaction between methacrolein and the nitrone -benzylidenphenylamine--oxide.