DUGi

Synthesis and Reactivity of Ruthenium Phosphite Indenylidene Complexes

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@8658

The synthesis of the four olefin metathesis precatalysts Caz-1a-d, featuring the NHC ligand N,N’-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) and four different phosphites (P((OPr)-Pr-i)(3), P(OPh)(3), P(OEt)(3), and P(OMe)(3)), is reported. The complexes are readily synthesized from commercially available [RuCl2(3-phenylinden-1-ylidene)-(pyridine)(SIMes)] (Ind-III) in yields of up to 88%. These complexes adopt an unusual cis configuration between the phosphite and the NHC ligands. NMR experiments and computational studies confirm that the cis complexes are thermodynamically favored in comparison to their trans counterparts. In addition, the isomerization from trans to cis occurs via a mononuclear and non-dissociative mechanism. Among the four precatalysts, cis-Caz-1a, featuring a P((OPr)-Pr-i)(3) ligand, displays the highest activity in ring-closing metathesis and cross-metathesis transformations. Experiments at low catalyst loadings demonstrated the potential of this catalyst, allowing better conversions than with commonly used commercially available precatalysts

We gratefully acknowledge the Royal Society (University Research Fellowship to C.S.J.C.), the EC (CP-FP 211468-2 EUMET and CIG09-GA-2011-293900), the Spanish MINECO (RYC-2009-05226 to A.P.) and the Catalan Government (BE-2011 to A.P.) for funding

American Chemical Society