Synthesis and dynamic behaviour of zwitterionic [M(η⁶-C₆H₅-BPh₃)(coe)₂] (M = Rh, Ir) cyclooctene complexes

Abstract

The synthesis and structural characterization of zwitterionic [(η(6)-C6H5-BPh3)M(coe)2] (M = Rh, Ir) cyclooctene complexes is described. Both complexes exhibit an unusual exo-endo conformation of both cyclooctene ligands in the solid state. However, an equilibrium between the endo-endo and exo-endo rotational isomers arising from the hindered rotation about the metal-cyclooctene bond is observed in solution. Rotational barriers of around 65 kJ mol(-1) (Rh) and 84 kJ mol(-1) (Ir) have been determined by 2D EXSY NMR spectroscopy. The rotation process has also been studied by DFT calculations that showed that the dynamic behaviour is a consequence of the oscillation of the cyclooctene ligands about the metal-olefin bond instead of completing a full rotation.

Synthesis and Structural Characterization of Tris(isopropylbenzimidazol-2-ylthio)methyl Zinc Complexes, [TitmPriBenz]ZnX: Modulation of Transannular Zn–C Interactions

“…The observation that [HB­(C 6 F 5 ) 3 ] − does not coordinate to the zinc center of the cation {[Titm Pr i Benz ]­Zn} + may be attributed to the sterically demanding nature of the ligand, as evaluated by its cone angle and percent buried volume (Table ). In addition, while [MeB­(C 6 F 5 ) 3 ] − is also known to exhibit weak interactions with metal centers via M···Me–B and M···F–C interactions, ,, the shortest Zn···H distance between the zinc center and the methyl group of [MeB­(C 6 F 5 ) 3 ] − (4.72 Å) is much greater than the sum of the van der Waals radii (3.59 Å), and so it is evident that the anion is also noncoordinating in this system. The value of 2.6 ppm for Δδ­( m,p -F), i.e.…”