Allenyl-germanes and-stannanes, Ph3MC (R)= C= CR′ R ″(M= Ge, Sn) can be obtained, generally in excellent yield, through alkylcopper (I)-induced 1, 3-substitution of the propargylic chlorides Ph3MCCCR′ R ″Cl. In the tin series, however transmetallation is the main process when MeCu, H2C= CHCu or PhCu are used. The allenyl compounds in which R is (trimethylsilyl) ethynyl or 4, 4-dimethyl-1, 2-pentadienyl can be obtained by using the ...