The first stable 3,1-germaphosphaallene Tip(t-Bu)GeCPAr

The first stable heteroallenic derivative with two heavy doubly-bonded Group 14 and 15 elements, the germaphosphaallene Tip(t-Bu)GeCPAr 1 (Tip=2,4,6-triisopropylphenyl, Ar=2,4,6-tri-tert-butylphenyl), has been prepared in a nearly quantitative yield by dechlorofluorination of Tip(t-Bu)Ge(F)C(Cl)PAr (obtained from ArPCCl2 and successive reaction with n-butyllithium and Tip(t-Bu)GeF2) with tert-butyllithium. 1 gives [2+2] cycloadducts by the GeC double bond with benzaldehyde, benzophenone and fluorenone to afford the corresponding germaoxetanes 11–13. 13 has been structurally characterized showing a long GeO bond (1.821(2) Å) and a slightly folded four-membered ring GeOCC (18.8° along C(1)Ge axis).