Synthesis, crystal structure and solution properties of a diastereomeric ( p-cymene)ruthenium(II) chiral Schiff base complex

• Published in: Polyhedron Vol. 21; no. 19; pp. 1929 - 1934
• Main Authors: Rath, Rakesh K, Nethaji, Munirathinam, Chakravarty, Akhil R
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.08.2002
• Subjects: 2D NMR; Absolute configuration; Arene ruthenium; CH–π interaction; Crystal structures; CH–π interaction; Crystal structures; Arene ruthenium; 2D NMR; Absolute configuration
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(02)01104-X

The reaction of [Ru(η 6- p-cymene)Cl 2] 2 with the chiral Schiff base ( S)-(α-methylbenzyl)-3,5-di- t-butylsalicylaldimine (HL*) in the presence of NEt 3 in CH 2Cl 2 forms a diastereomeric mixture of ( R Ru, S C)- and ( S Ru, S C)-[Ru(η 6- p-cymene)(L*)Cl] ( 1a, 1b). The crystal structure of the complex shows the presence of both the diastereomers in a 1:1 ratio in the triclinic space group P1. Both the structures exhibit the presence of a non-covalent CH–π interaction involving two p-cymene ring protons and the phenyl group attached to the chiral carbon. The 1H NMR spectra of the complex in CDCl 3 display the presence of two diastereomers in a 88:12 ratio at room temperature. The absolute configuration of the major diastereomer in solution has been determined by 2D NOE measurements. Observation of NOE cross peaks involving the C*H and the p-cymene ring protons indicates a ( R Ru, S C)- configuration of the major diastereomer in solution. The arene ruthenium(II) complex [(η 6- p-cymene)Ru{2-O-(3,5-di- t-Bu)C 6H 2CHNCH(Me)Ph}Cl], whose crystal structure shows the presence of two diastereomers having ( R Ru, S C)- and ( S Ru, S C)- configurations in a 1:1 ratio and the 1H NMR in CDCl 3 displays the presence of two diastereomers in a 88:12 ratio, has been unequivocally analyzed to have a ( R Ru, S C)- configuration for the major diastereomer in solution by 2D NMR spectroscopy.