Boosting Low Valent Al(I) Reactivity with a Potassium Reagent.

: It was anticipated that the potassium reagent RK (R = CH(SiMe3)2 or N(SiMe3)2) reacts with the low-valent Al(I) complex (DIPPBDI)Al (DIPPBDI = HC[C(Me)N(DIPP)]2, DIPP = 2,6-iPr-phenyl) to the anionic Al complex [(DIPPBDI)AlR]-K+. However, instead deprotonation of the Me group in the ligand backbone was observed and the Al(I) complex [H2C=C(N-DIPP)-C(H)=C(Me)-N-DIPP]Al-K+ crystallized as a bright-yellow product (1, 73%). Like most anionic Al(I) complexes, also 1 forms a dimer in which formally negatively charged Al centers are bridged by K+ ions that show strong K+···DIPP interactions. The rather short Al-K bonds (3.499(1)-3.588(1) A) indicate tight bonding of the dimer. According to DOSY NMR, complex 1 is dimeric in benzene and monomeric in THF but slowly reacts with both solvents. In reaction with benzene, double C-H bond activation is observed and exclusively a product with a para-phenylene moiety was isolated. DFT calculations confirm that the anionic Al center in 1 is much more reactive than that in the parent complex (DIPPBDI)Al. Calculations on a full dimeric model system show that both metals, the Al(I) center and the K+ ion, work in concert. Synergy between these metals determines the reactivity of 1.