Chiral recognition of amino esters by ruthenium porphyrin complexes and crystal structure of {5,10,15,20-tetrakis[o-(3,3,3-trifluoro-2-methoxy-2-phenylpropanoylamino)phenyl]porphyrin}bis(L-valine methyl ester)ruthenium(II) (α,α,β,β isomer)

Abstract

Bis(amino ester)ruthenium(II) picket-fence complexes bearing optically active α-methoxy-α-(trifluoromethyl)phenylacetyl residues on both sides of a porphyrin plane (α,β,α,β and α,α,β,β isomers) have been synthesized. These chiral porphyrins have been characterized by UV-visible, IR and ¹H, ¹⁹F NMR spectroscopy. For the valine methyl ester complex a chiral recognition was observed for the oxidation of the ligand yielding a mixed ligated imino ester/amino ester ruthenium(II) complex with 66% enantiomeric excess. The chiral recognition involving ligated amino ester complexation and oxidation to give imino complexes is discussed. The crystal structure of the complex α,α,β,β-[Ru(P){(CH₃)₂CHCH(NH₂)CO₂CH₃}₂] {P = 5,10,15,20-tetrakis[o-(3,3,3-trifluoro-2-methoxy-2-phenylpropanoylamino)phenyl]porphyrinate} was determined.