Grubbs-type ruthenium alkylidene

A Grubbs-type ruthenium complex and a Hoveyda ruthenium complex were compared under similar conditions for recycled activity. Both the reference catalysts showed a large drop in metathesis activity in the subsequent tests. For example, a Grubbs-type ruthenium alkylidene catalyst showed a drop of nearly 50% conversion in the second run. 

Grubbs-type ruthenium alkylidenes have been shown to be catalytically active for ring-closing olefin metathesis in ILs such as [G4GiIm]PE6 and [G4GiIm]GF3S03, but their catalytic reactivity rapidly vanished in subsequent recycling runs and reuse. " ... 

Because the key to control of molecular weight distribution depends on the relative rates for initiation and propagation, studies to control these relative rates have been conducted. Studies with the Grubbs-type ruthenium carbene complexes have shown that the ruthenium benzylidene complexes undergo faster initiation than vinyl alkylidene... 

The two most commonly used single-site catalysts for ADMET today are (1) Schrock s alkylidene catalysts of the type M(CHR )(NAr )(OR)2 where M = W or Mo, AC = 2, 6-C6H3-/-Pr2, R = CMe2Ph, and R = CMe(CF3)2 (14)7 and (2) Grubbs ruthenium-based catalyst, RuCl2(=CHPh)(PCy3)2 (12) where Cy = cyclohexyl.9 While both catalysts meet the requirements to be successful in ADMET, they are markedly different in their reactivity and in die results each can produce. 

Oxoalkylidene complexes of the type (W=CH-CH=CPh2)(0)[0CMe(CF3)2]2 L (16) were obtained by Grubbs and utilized for ROMP of norbomene [159]. His synthetic strategy employed 3,3-diphenylcyclopropene for the synthesis of the alkylidene moiety [159,160]. This method was later adapted for the synthesis of the first well-defined ruthenium metathesis initiators [161]. Furthermore, (0Ar)2W(CH-/-Bu)(0)(PMe3) (17) was synthesized by Schrock et al. and reported to polymerize 2,3-dicarbomethoxynor-bornadiene in a living manner [162]. 

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