Control of the migratory aptitudes of vinyl and aryl ligands in ruthenium(II) complexes

• Published in: Inorganica Chimica Acta 1995-12, Vol.240 (1), p.263-271
• Main Authors: Waugh, Martin P., Mawby, Roger J., Reid, Amanda J., Carter, Richard J., Reynolds, Colin D.
• Format: Article
• Language: English
• Subjects: Crystal structures; Migration; Ruthenium complexes; Vinyl and aryl ligand
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/0020-1693(95)04542-2

Complexes Ru(CO) 2 (CH=CHR) (C 6H 4X-4)L 2 (R= tBu, Ph, OEt; X=H, Cl, OMe; L=PMe 3, PMe 2Ph, P(OMe) 2Ph) in which the two phosphorus ligands are mutually cis (isomer 1) react readily with ligands tBuNC, CO and P(OMe) 3 to give complexes in which one of the organic ligands has migrated onto a carbonyl ligand. Vinyl migration products ( 5) retain the mutually cis geometry of the phosphorus ligands, and are unstable: one of the decomposition products is the ketone RCH=CHC(O)C 6H 4X-4. Phenyl migration products ( 4) are stable and have the phosphorus ligands in mutually trans positions; an X-ray crystal structure of Ru(CO) (CN tBu) {C(O)Ph} (CH=CHPh) (PMe 2Ph) 2 was obtained. In both cases, the incoming ligand enters trans to the newly formed acyl ligand. Vinyl migration is favoured over aryl migration by electron-donating substituents on the vinyl ligand, electron-withdrawing substituents on the aryl ligand, good σ-donor phosphorus ligands and use of tBuNC as the incoming ligand. The rate of phenyl migration in Ru(CO) 2(CH=CHPh)Ph(PMe 2Ph) 2 is independent of tBuNC concentration: k=1.5 × 10 −3 s −1 at 20°C. Isomer 3 of complexes Ru(CO) 2(CH=CHR) (C 6H 4X-4)L 2 in which the phosphorus ligands are mutually trans is much less reactive towards migration reactions. The reactivity of isomer 1 is attributed to the steric strain of two mutually cis phosphorus ligands.