Cyclo‐Dipnictadialanes

Abstract

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 (IiPr₂ )Al(μ-PPh)]₂ .