Boosting Low‐Valent Aluminum(I) Reactivity with a Potassium Reagent

Abstract

The reagent RK [R=CH(SiMe 3 ) 2 or N(SiMe 3 ) 2 ] was expected to react with the low‐valent ( DIPP BDI)Al ( DIPP BDI=HC[C(Me)N(DIPP)] 2 , DIPP=2,6‐ i Pr‐phenyl) to give [( DIPP BDI)AlR] − K + . However, deprotonation of the Me group in the ligand backbone was observed and [H 2 C=C(N‐DIPP)−C(H)=C(Me)−N−DIPP]Al − K + ( 1 ) crystallized as a bright‐yellow product (73 %). Like most anionic Al I complexes, 1 forms a dimer in which formally negatively charged Al centers are bridged by K + ions, showing strong K + ⋅⋅⋅DIPP interactions. The rather short Al–K bonds [3.499(1)–3.588(1) Å] indicate tight bonding of the dimer. According to DOSY NMR analysis, 1 is dimeric in C 6 H 6 and monomeric in THF, but slowly reacts with both solvents. In reaction with C 6 H 6 , two C−H bond activations are observed and a product with a para ‐phenylene moiety was exclusively isolated. DFT calculations confirm that the Al center in 1 is more reactive than that in ( DIPP BDI)Al. Calculations show that both Al I and K + work in concert and determines the reactivity of 1 .