Germylene Reactions with Quinones Shed Light on Germylene Phenone Equilibria

Ge[CH(SiMe3)2]2 (1) and Ge[N(SiMe3)2]2 (2) react with anthraquinone and naphthoquinone
in a 2:1 ratio to form five-membered rings with the carbonyl oxygens and the ortho carbons
of the adjacent aromatic ring. The reaction with 1,4-diacetylbenzene proceeds in a similar
fashion with 1; however no reaction is observed with 2. Compounds 1 and 2 react with 1,2-diacetylbenzene to yield a novel bicyclo species. In a previous report describing equilibria
between 1 and phenones, it appeared that 2 did not undergo reaction to generate the five-membered ring with the accompanying formation of a conjugated triene. However, these
quinone results indicate that an equilibrium can exist between 2 and a phenone moiety. In
the reaction with quinones, a second equivalent of germylene effectively traps the conjugated
triene by undergoing a 1,4-addition reaction. Unlike the initial triene formation, this second
insertion is irreversible.