Monovalent group 13 diyls are versatile reagents in oxidative addition reactions. We report here [1,4]-cycloaddition reactions of β-diketiminate-substituted LM (M = Al, Ga, In, Tl; L HC[C(Me)NDipp]2, Dipp 2,6-iPr2C6H3) with various 1,2-diketones to give 5-metalla-spiro[4.5]heterodecenes 1, 4–6, and 8–10, respectively. In contrast, the reaction LTl acenaphthenequinone gave [2,3]-cycloaddition pr...