Resolution of racemic amino acids via stereoselective ligand-exchange reactions on an optically pure nickel(II) complex

Abstract

Racemic amino acids (Ala, Val, Leu) co-ordinate steroselectively to the square-planar chiral matrix complex [Ni{(S,S)-L)}]²⁺{(S,S)-L =N,N′-bis[(2S)-pyrrolidin-2-yl]propane-1,3-diamine}. The stereoselectivities [Ala, 60%(S), 40%(R); Val, 75%(S), 25%(R); Leu, 68%(S), 32%(R)] have been predicted by molecular mechanics calculations and determined experimentally by potentiometric titrations. The structure of the chiral matrix complex has also been determined: orthorhombic, space group P2₁2₁2₁, a= 8.298(3), b= 13.513(4), c= 18.293(7)Å, Z= 4, R′= 0.051.