π-Facial selectivities in the coordination of an optically pure fused cyclopentadienyl ligand to arene ruthenium moieties. NMR spectral and structural characterization of a single diastereomer of [(PCp)Ru(Me 6C 6)]PF 6

Abstract

Optically pure thallium (1 R)-(−)-9,9-dimethyltricyclo[6.1.1.0 2′6]deca-2,5-dienide (TIPCp) reacts with [( n 6-arene)RuCl 2] 2 (arene = C 6H 6, MeC 6H 4, p-MeC 6H 4CHMe 2, Me 6C 6) and NH 4PF 6 to form two isomers of the complexes [( n 5-PCp)Ru( n 6-arene)]PF 6. The π-facial stereoselectivity for coordination of PCp is a function of the steric bulk of the arene increasing from a 1:1 (C 6H 6) to a 14:1 (Me 6C 6) exolendo isomer ratio. New complexes were characterized by elemental analyses, physical properties, differential pulse voltammetry and 1H and 13C{ 1H} one- and two-dimensional NMR spectroscopy. The structure of [( n 5-PCp)Ru( n 6-Me 6C 6)]PF 6 was confirmed by X-ray crystallography. This compound crystallized in the acentric space group C222 1 in a unit cell with the following dimensions: a = 11.451(4), b = 13.426(5), c = 31.249(3) Å, V= 4804(3) Å 3, Z = 8. Refinement converged to R(F) = 0.056 for 1723 independent observed ( I>3σ( I)) reflections. Ruthenium coordinates to the less sterically hindered exo face of the PCp ligand, anti to the gem-dimethyl group, and is closer to the arene (Ru-ring centroid = 1.73 Å) than to the PCp ligand (Ru-ring centroid = 1.79 Å).