Mixed N‑Heterocyclic Carbene/Phosphite Ruthenium Complexes: The Effect of a Bulkier NHC.

The
synthesis, characterization, and catalytic activity of two
new complexes, 2a,b, featuring a sterically
demanding NHC and two different phosphites are described. Complexes 2a,b display a mutually trans arrangement of
the π-acidic phosphite and the strong σ-donor SIPr ligand
(SIPr = N,N′-bis­(2,6-diisopropylphenyl)­imidazolin-2-ylidene).
The synergy between the phosphite and the NHC ligand was revealed
in the RCM of challenging substrates leading to tetrasubstituted olefins
where, in comparison to their phosphine-containing analogues, 2a,b allowed higher conversions of these challenging
substrates.