Phosphanylalanes and Phosphanylgallanes Stabilized only by a Lewis Base

The synthesis and characterization of the first parent phosphanylalane and phosphanylgallane stabilized only by a Lewis base (LB) are reported. The corresponding substituted compounds, such as IDipp?GaH₂PCy₂ ( 1 ) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐ylidene) were obtained by the reaction of LiPCy₂ with IDipp?GaH₂Cl. However, the LB‐stabilized parent compounds IDipp?GaH₂PH₂ ( 3 ) and IDipp?AlH₂PH₂ ( 4 ) were prepared via a salt metathesis of LiPH₂?DME with IDipp?E′H₂Cl (E′=Ga, Al) or by H₂‐elimination reactions of IDipp?E′H₃ (E′=Ga, Al) and PH₃, respectively. The compounds could be isolated as crystalline solids and completely characterized. Supporting DFT computations gave insight into the reaction pathways as well as into the stability of these compounds with respect to their decomposition behavior.