Rearranged ylide ligand

The interaction between hydride and ylide ligands in the complex, [W(H)(CH2=PMe2Ph)Cp2][PP6], has been studied.57 On heating in acetone, the complex is transformed into [W(Me)(PMe2Ph)Cp2)[PF6]. Based on kinetic studies, two alternative mechanisms for the rearrangement were proposed. One involves the formation of an agostic methyl intermediate, [W(CH2)(p-H)Cp2], and the other involves an equilibrium between a carbene hydride, [W(CH2)(H)Cp2]+, and a methyl cation, [W(CH3)Cp2]... 

On the other hand, a Gu(i)/chiral diimine complex in the cyclic ylide formation/[2,3]-sigmatropic rearrangement has been examined by Clark and co-workers (Equation (3)). Up to 57% ee has been obtained when C2-symmetric ligand 32 is used. 

A detailed examination of the reactivity of organo-aluminium derivatives of 0,0-bifunctional ligands has been undertaken,559 and the effect of substituents on the reversible rearrangements of chlorophosphane-dichlorogermylene ylides to trichloro-germylphosphanes has been investigated.560... 

In the rhodium-catalyzed formation of oxonium ylides of type 63, an asymmetric [2,3]-rearrangement has been achieved. When Wphthaloyl-(3 )-/( tt-leucine was used as ligand, an ee of up to 60% was obtained (Scheme 100) <1997TL4705>. 

The sulfur ylides 254 used in the stereoselective [2,3]-sigmatropic rearrangement are generated by copper(I)-catalyzed Doyle-Kirmse reaction of aryl sulfides 253 and diazo compounds bearing Oppolzer s camphor sultam auxiliary 252 in the presence of chiral diamine ligand S, S)-259 <05JA15016>. These intermediate ylides undergo spontaneous... 

Ligand variation on the metal center can also modulate product distribution. West and coworkers evaluated diazoketone 30, which is capable of both five- and six-membered ylide formation. Under copper catalysis, where both five- and six-membered ylides are readily formed, they found that Cu(tfacac)2 favored the six-membered ylide formation/[2,31-rearrangement pathway to afford 31. Conversely, Cu(hfacac)2 favored the five-membered ylide formation/[l,2]-shift pathway, providing 32. Though the differing reactivity preference for Cu(tfacac)2 is not understood, Ae result is consistent and can be applied synthetically where appropriate. 

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