Isolation and structural characterisation of [{(Me3Si)(2)NMg[mu-OC(H)Ph-2]center dot(O=CPh2)}(2)], an intermediate in the beta-hydride transfer reaction between an aklyl(amido)magnesium and benzophenone

The in situ reaction of Bu2Mg with 2 mel. equiv, of (Me3Si)(2)NH followed by addition of Ph2CO yields the heteroleptic amide/alkoxide complex [{Me3Si)(2)NMg[mu-OC-(H)Ph-2].(O=CPh2)}(2)] 1, whereas reaction of purified [{(Me3Si)(2)N}(2)Mg] 2 with Ph2CO results in formation of the solvate [{(Me3Si)(2)N)(2)Mg .(O=CPh2)(2)] 3, the difference being due to incomplete amination of the bis(alkyl)magnesium compound resulting in beta-hydride transfer to the ketone, which is the first example of this type of transformation using an alkyl(amido)magnesium reagent.