Tetraorganoindium ate complexes, prepared by the addition of organolithium reagents to trialkylindium, reacted with alpha,beta-unsaturated ketones in a 1,4-addition fashion; allylic indates derived from allylic indium sesquihalides coupled with allylic halides regio- and stereo-specifically to give high yields of head-to-tail 1,5-dienes.