Alkylidene-Ruthenium-Tin Catalysts for the Formation of Fatty Nitriles and Esters via Cross-Metathesis of Plant Oil Derivatives

The reaction of SnCl2 with the Ru−Cl bond of
the Grubbs I catalyst RuCl2(CHPh)(PCy3)2 (1) gives the complex {[Ru(CHPh)(SnCl3)(PCy3)]2(μ-Cl)3}−[HPCy3]+ (2), but
containing two diethyl ether solvate molecules. The formal insertion
of SnCl2 into one Ru−Cl bond of the Hoveyda II catalyst
RuCl2(CH-C6H4OPri)(H2IMes) (3) (H2IMes = N,N′-dimesityl-4,5-dihydroimidazol-2-ylidene)
results in formation of the new complex RuCl(SnCl3)(CH-C6H4OPri)(H2IMes) (4). The X-ray analyses of 2 and 4 show the presence of very short Ru−Sn bonds (2.5834(9)
Å mean bond for 2 and 2.5925(12) Å for 4) and the retention of short RuC bonds (1.895(10)
and 1.825(8) Å, respectively). Complex 4 shows an
excellent catalytic activity for the cross-metathesis of plant oil
derivatives, the C11 ω-unsaturated ester and aldehyde and the
unsaturated C18 diester with acrylonitrile, and a good activity for
their cross-metathesis with methyl acrylate. Good to excellent yield
of α,ω-bifunctional compounds, precursors of polyesters
and polyamides, were obtained. Complex 2 shows catalytic
activity for the self-metathesis of C11 ω-unsaturated aldehyde
at low concentration to produce C20 α,ω-dialdehyde.