Reactivity of Bis(organoamino)phosphanes with Aluminum(III) Compounds: Straightforward Access to Diiminophosphinates by Means of Hydrogen‐Atom Migration – An Experimental and Theoretical Study

The reactivity of bis(organoamino)phosphanes PhP(NHR)(NHR′) ( 1a – 1c , in which R, R′ = t Bu for 1a ; t Bu, Dip for 1b ; and Ph for 1c ; Dip = C 6 H 3 –2,6‐ i Pr 2 ) and t BuP(NHDip) 2 ( 1d ) with Me 3 Al was investigated. The reaction of 1a or 1b gave in the first step compounds [PhP(NHR)(NR′)]AlMe 2 (in which R, R′ = t Bu for 2a ; t Bu, Dip for 2b ) as a result of methane elimination that upon heating underwent nitrogen‐to‐phosphorus hydrogen‐atom migration under the formation of diiminophosphinates [Ph(H)P(NR)(NR′)]AlMe 2 (in which R, R′ = t Bu for 3a ; t Bu, Dip for 3b ). In contrast, phosphane 1c showed a reversed reaction sequence that yielded an intermediate [Ph(H)P(NHPh)(=NPh)]AlMe 3 ( 2c ) first as a consequence of hydrogen‐atom migration followed by the methane elimination and formation of diiminophosphinate [Ph(H)P(NPh) 2 ]AlMe 2 ( 3c ). The partial deprotonation of 1a , b , d using one molar equivalent of n BuLi followed by the treatment with AlCl 3 smoothly produced compounds [Ph(H)P(NR)(NR′)]AlCl 2 (in which R, R′ = t Bu for 4a ; t Bu, Dip for 4b ) and [ t Bu(H)P(NDip) 2 ]AlCl 2 ( 4d ), in which the hydrogen atom was again shifted from the nitrogen to the phosphorus atom. All studied compounds were characterized with the help of elemental analysis; 1 H, 13 C{ 1 H}, 31 P, and 31 P{ 1 H} NMR spectra; and in the case of 3c , 4a , 4b , and 4d by using single‐crystal X‐ray diffraction analysis. The phenomenon of the hydrogen‐atom migration was subjected also to a theoretical survey with particular emphasis on the influence of the phosphane used.