Dimetallation allenes

Reaction of Me3GeCl with a substituted cyclopropene in the presence of lithium diisopropylamide (LDA) yields different products depending on the order of addition of the reagents.97 Addition of LDA to a mixture of the reactants gives the dimetallated cyclopropene (Equation (76)). Dilithiation of the cyclopropane followed by addition of Me3GeCl gives the allene (Equation (77)). 

Similar to the abovementioned silver nhc coordination compounds, carbene chemistry has also been dominant in the field of gold organometallic chemistry. Noteworthy examples include a Au(PPh3)-compound derived from tetraaminoallene, that can be rationalised in terms of a dicarbene with ylide character and which, owing to the electron-rich character of the central carbon atom, offers the potential for dimetallation products.108 Non-activated allenes and alkynes have been found by Lavallo to be readily aminated by cationic carbene gold complexes.109 For this purpose, a 2,6-diisopropylphenyl functionalized cyclic alkylaminocarbene gold(I) complex... 

Pd-catalyzed dimetallation of allenes with dimetallic reagents has been studied extensively. For example, regioselective 1,2-disilylation of alkylallene gave 139 [44]. 

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