Jay C. Conrad

Ligand manipulation and design for ruthenium metathesis and tandem metathesis-hydrogenation catalysis

Results of investigations into tandem ring-opening metathesis polymerization (ROMP)-hydrogenation are reviewed, in which hydrogen and 3-chloro-3-methyl-1-butyne provide simple chemical toggles to switch between metathesis and hydrogenation chemistry, enabling multiple tandem catalysis in chlorocarbon solvent. In the presence of methanol, hydrogenation of metathesis polymers can be carried out under 1 atm H 2 . Issues of ligand design are examined in developing new Ru-diphosphine catalysts with improved selectivity, and an important decomposition pathway is identified for RuCl 2 (PP)(CHR) systems (PP = chelating diphosphine).

The kinetic instability of σ-bound aryloxide in coordinatively unsaturated or labile complexes of ruthenium

Abstract Reaction of RuCl2(PPh3)3 (1) or RuHCl(PPh3)3 (2) with KOAr (Ar=4-tBuC6H4) in non-alcohol solvents affords π-aryloxide derivatives Ru(η5-ArO)(o-C6H4PPh2)(PPh3) (3a) or RuH(η5-ArO)(PPh3)2 (6a), respectively. The phenoxide analogues 3b and 6b are obtained on use of KOPh or TlOPh. Treatment of 1 with 1 equiv. KOAr in the presence of isopropanol liberates the phenol and acetone, affording clean 2 in quantitative yields. In 3:1 methanol–CH2Cl2, RuHCl(CO)(PPh3)3 (4) is also formed in small amounts. Reaction of 1 with 2 KOAr in 20% MeOH–CH2Cl2 affords a mixture of 6a and RuH2(CO)(PPh3)3 (5). In the corresponding reaction of 2 with 1 KOAr, σ–π isomerization of the σ-aryloxide ligand dominates, affording 6a·MeOH as the principal product. Treatment of 6a with ethereal HCl gives [RuH(η6-ArOH)(PPh3)2]Cl (7a); the corresponding reaction of 6b yields RuCl(η5-PhO)(PPh3)2 (8b). The crystal structures of 3a, 3b, 4, 5, 7a, and 8b are reported.

An Attractive Route to Olefin Metathesis Catalysts: Facile Synthesis of a Ruthenium Alkylidene Complex Containing Labile Phosphane Donors

Reaction of RuHCl(PPh3)34 with 3-chloro-3-methyl-1-butyne effects transformation into RuCl2(PPh3)2(CHCHCMe2) 1c. Starting 4 is available commercially, or via quantitative reaction of RuCl2(PPh3)3 with one equivalent of alkali phenoxides or isopropoxides in refluxing benzene-2-propanol. Phosphane exchange between 1c and PCy3 or 1,3-(CH2PCy2)2C6H4 is rapid at RT, affording RuCl2(PCy3)2(CHCHCMe2) 1b or the novel alkylidene complex RuCl2[1,3-(CH2PCy2)2C6H4](CHCHCMe2) 7. Much slower exchange occurred on use of RuCl2(PCy3)2(CHPh) (1a) as precursor. Complex 1c is stable indefinitely (months) in the solid state at RT under N2, but dimerizes slowly in solution to give RuCl(PPh3)2(μ-Cl)3Ru(PPh3)2(CHCHCMe2) 6a. 2,7-Dimethyl-octa-2,4,6-triene, the formal product of carbene coupling, is observed by 1H NMR. Dimerization does not compete with phosphane exchange. A side-product arising from use of excess 3-chloro-3-methyl-1-butyne in the synthesis of 1c was identified as Ru(IV) carbyne complex RuCl3(PPh3)2(≡CCHCMe2) 5, the structure of which was confirmed by X-ray crystallography.

A Ru-isocyanate initiator for fast, living, precisely controlled ring-opening metathesis polymerization at ambient temperatures

The new complex Ru(NCO)(2)(IMes)(py)(2)(=CHPh) is the first ruthenium metathesis initiator capable of fast, controlled living polymerization of functionalized norbornenes at room temperature, irrespective of monomer bulk.