Ronald J. McKinney

Linear dimerization of acrylates by palladium and rhodium catalysts: effect of lewis and protic acid additives

Abstract The rates of catalytic dimerization of alkyl acrylates by PdCl 2 (NCPh) 2 and by [(C 2 H 4 )RhCl] 2 are greatly increased by the combination of a Lewis acid promoter and a proton source. For the rhodium systems, catalyst life was also enhanced and yields of up to 280 mol/mol Rh with > 98% selectivity to linear dialkyl hexenedioates have been observed. Optimal conditions involved the use of [(C 2 H 4 ) 2 RhCl] 2 , FeCl 3 and methanol in the proportions 1:5:10 at 80 °C. The isomeric composition of the product is markedly influenced by the combination of catalyst and promoter employed; either cis -Δ 2 , trans -Δ 2 , or trans -Δ 3 hexenedioate may predominate. Thus on changing the promoter from FeCl 3 to SnCl 4 in the Rh-catalyzed system, the product distribution changed from 85% trans -Δ 2 to 62% cis -Δ 2 hexene-dionate; certain Pd-catalyzed systems produced up to 60% of the isomeric Δ 3 hexenedioates.

Hydrocarbon complexes of iron, ruthenium, and osmium. Part 13. The chemistry of dicarbonyl(trimethylsilyl)(1—3;6—7-η-8-endo-trimethyl-silycyclo-octatrienyl)ruthenium, a pentalene precursor

Reactions of [Ru(SiMe3)(CO)2{1–3;6–7--C8H8(8-endo-SiMe3)}] with the compounds [Ru(SiMe3)2(CO)4], [Ru2(SiMe3)2(CO)8], or [Ru3(CO)1212] give triruthenium pentalene complexes [Ru3(CO)8{C8H6–n(SiMe3)n}](n= 0–2). Also formed are two closely related diruthenium complexes [Ru2(SiMe3)(CO)5(C8H8SiMe3)] and [Ru2(SiMe3)(CO)4(C8H8SiMe3)]; the former contains a cyclic η7–C8 ligand which ring-opens on thermolysis to yield an η8–C8 ligand in the latter. Reactions of [Ru(SiMe3)(CO)2{1–3;6–7-η-C8H7(SiMe3)2–5,8}] with the same reagents give only the pentalene complexes [Ru3(CO)8{C8H6–n(SiMe3)n}](n= 0–3), but in increased yields. Heterodimetallic complexes [FeRu(SiMe3)(CO)5(C8H8SiMe3)] and [MnRu(CO)7(C8H7)] are obtained on treating [Ru(SiMe3)(CO)2{1–3;6–7-η-C8H8(8-endo-SiMe3)}] with [Fe2(CO)9] or [MnMe(CO)5], respectively.