Stabilities and Limitations in the Reactivity of Phosphorus Ylide‐Based Aluminum– and Gallium–Carbon Ambiphiles: A Combined Experimental and Computational Approach

The unexpected reactivity and stability limits of phosphorus ylide‐based aluminum– and gallium–carbon ambiphiles are described. While the previously published t ‐butyl‐substituted compound (2‐{Al t Bu 2 }‐C 6 H 4 )Ph 2 PCMe 2 ( 1 tBu ) reacts reversibly with NH 3 at room temperature (RT) with cleavage of a NH bond, the reaction with MeNH 2 is much less favorable and proceeds irreversibly only at 90 °C. All other title compounds 1 R with R = Me, Et, Mes, and C 6 F 5 decompose in the presence of NH 3 . The decomposition of 1 Et in the presence of ammonia can be well followed by nuclear magnetic resonance (NMR) spectroscopy. All title compounds remain stable in the presence of t ‐BuNH 2 and Et 2 NH. In addition, an unexpected reactivity is found in the reaction of 1 R and the gallium analogues 2 R with isocyanates. Instead of yielding the expected ring‐expansion products, the title compounds catalyze the trimerization of isocyanates. Also the reactivity toward MeOH and H 2 O is presented. Quantum chemical calculations show that activation of the OH bonds should be feasible at RT. Experimental findings, however, only show the decomposition of 1 tBu in the corresponding reactions. Nevertheless, the cleavage of the OH bond is feasible and affords the activation products 7 and 8 starting from the ammonia activation product 3 .