Synthesis and Characterization of Primary Aluminum Parent Amides and Phosphides

The synthesis and characterization of the sterically crowded primary alanes (Ar iPr4 AlH2)2 (Ar iPr4 = C6H3-2,6(C6H3-2,6- i Pr2)2) and (Ar iPr8 AlH2)2 (Ar iPr8 = C6H-2,6(C6H2-2,4,6- i Pr6)2-3,5- i Pr2) are described. They, along with their previously reported less-hindered analogue (ArMe6 AlH2)2 (ArMe6 = C6H3-2,6(C6H2-2,4,6-Me3)2), were reacted with ammonia to give the parent amido alanes {Ar x Al(H)NH2}2 (Ar x = ArMe6 , 1; Ar iPr4 , 2; Ar iPr8 , 3), which are the first well-characterized hydride amido derivatives of aluminum and are relatively rare examples of parent aluminum amides. In contrast, the reaction of (ArMe6 AlH2)2 with phosphine yielded the structurally unique Al/P cage species {(ArMe6 Al)3(μ-PH2)3(μ-PH)PH2} (4) as the major product and a smaller amount of {(ArMe6 Al)4(μ-PH2)4(μ-PH)} (5) as a minor product. All compounds were characterized by NMR and IR spectroscopy, while compounds 2–5 were also characterized by X-ray crystallography.