Reactivity of dialumane and "dialumene" compounds toward alkenes

The reactions of dialumane [L(thf)Al-Al(thf)L] (1, L=[{(2,6-iPr ₂C₆H₃)NC(Me)}₂]^2-) with stilbene and styrene afforded the oxidation/insertion products [L(thf)Al(CH(Ph)-CH(Ph))AlL] (2) and [L(thf)Al(CH(Ph)-CH₂)Al(thf)L] (3), respectively. In the presence of Na metal, precursor 1 reacted with butadienes, possibly through the reduced "dialumene" or the "carbene-like":AlL species, to yield aluminacyclopentenes [LAl(CH ₂C(Me)=C(Me)CH₂)Na]_n (4 a) and [Na(dme) ₃][LAl(CH₂C(Me)=CHCH₂)] (4 b, dme=dimethoxyethane) as [1+4] cycloaddition products, as well as the [2+4] cycloaddition product 1,6-dialumina-3,8-cyclodecadiene, [{Na(dme)} ₂][LAl(CH₂C(Me)=C(Me)CH₂)₂AlL] (5). The possible mechanisms of the cycloaddition reactions were studied by using DFT computations.