Cyclo‐Dipnictadialanes

Using the Al(I) precursor Cp(3t)Al in conjunction with triphosphiranes (PAr)(3) (Ar=Mes, Dip, Tip) we have succeeded in preparing Lewis base‐free cyclic diphosphadialanes with both the Al and P atoms bearing three substituents. Using the sterically more demanding Dip and Tip substituents the first 1,2‐diphospha‐3,4‐dialuminacyclobutanes were obtained, whereas with Mes substituents [Cp(3t)Al(μ‐PMes)](2) is formed. This divergent reactivity was corroborated by DFT studies, which indicated the thermodynamic preference for the 1,2‐diphospha‐3,4‐dialuminacyclobutane form for sterically more demanding groups on phosphorus. Using Cp*Al we could extend this concept to the corresponding cyclic diarsadialanes [Cp*Al(μ‐AsAr)](2) (Ar=Dip, Tip) and additionally add the phosphorus variants [Cp*Al(μ‐PAr)](2) (P=Mes, Dip, Tip). The reactivity of one variant [Cp(3t)Al(μ‐PPh)](2) towards NHCs was tested and resulted in double NHC‐stabilised [Cp(3t)(IiPr(2))Al(μ‐PPh)](2).