Crystal Structure and Computational Investigation of an Analogue of Grubbs’ Second Generation Catalyst with a Fluorous Phosphine

A fluorous phosphine analogue of Grubbs’ second
generation olefin metathesis catalyst, (H2IMes)­((Rf8(CH2)2)3P)­(Cl)2Ru­(=CHPh) (1; H2IMes/Rf8 = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene/(CF2)7CF3) is crystallized and the X-ray
structure analyzed in detail. The bond lengths and angles about ruthenium
are compared to those of two solvates and five derivatives of Grubbs’
second generation catalyst. All exhibit distorted square pyramidal
geometries in which the alkylidene ligands occupy apical positions,
and geometric trends are interpreted with the help of density functional
calculations. The perfluoroalkyl groups (1) exhibit helical conformations,
as manifested by various torsional relationships, (2) segregate in
the lattice, and (3) align in pairs of opposite helical chiralities.