An Aluminum Hydride That Functions like a Transition‐Metal Catalyst

Abstract

The reaction of [LAlH2 ] (L=HC(CMeNAr)2 , Ar=2,6-iPr2 C6 H3 ) with MeOTf (Tf=SO2 CF3 ) resulted in the formation of [LAlH(OTf)] (1) in high yield. The triflate substituent in 1 increases the positive charge at the aluminum center, which implies that 1 has a strong Lewis acidic character. The excellent catalytic activity of 1 for the hydroboration of organic compounds with carbonyl groups was investigated. Furthermore, it was shown that 1 effectively initiates the addition reaction of trimethylsilyl cyanide (TMSCN) to both aldehydes and ketones. Quantum mechanical calculations were carried out to explore the reaction mechanism.

Bis(4‐methylbenzoxazol‐2‐yl)methanide in s‐Block Metal Coordination

“…We embarked on extending the main‐group chemistry, fired by the ubiquitous β‐diketiminate ligand and its derivatives, to related bis(heterocyclo)methane and amine ligand systems. Starting from dipyridylmethane and ‐methanides ( A in Scheme ) we extended the ligand class to the dipyridylamides, ‐phosphanides, and ‐arsenides ( B ) .…”

LiAlH4: From Stoichiometric Reduction to Imine Hydrogenation Catalysis

“…[23] Also the last s-bond metathesis step in the cycle seemed questionable.Acomprehensive calculational study, however, demonstrated that the metal hydride mechanism shown in Scheme 1isfeasible. [15,18,[31][32][33][34][35][36][37][38][39][40][41][42] Especially noteworthy are two very recent investigations on LiAlH 4 -catalyzed alkene and aldehyde/ketone hydroboration. Acrucial step is the hydrogenolysis of the metal À Cbond by H 2 ,for which the rate is known to decrease with decreasing bond ionicity:N a À C > Mg À C > Al À C. [25] since it is well-known that RNH 2 and R 2 NH react smoothly with LiAlH 4 to give aluminium amide products and H 2 , [26][27][28][29][30][31] hydrogenolysis of AlÀNbonds to give amines is anticipated to be even more cumbersome.S ubstitution of H 2 for polar borane or silane reductants was therefore al ogical step.…”

Comparing Neutral (Monometallic) and Anionic (Bimetallic) Aluminum Complexes in Hydroboration Catalysis: Influences of Lithium Cooperation and Ligand Set

“…Roesky and coworkers demonstrated that a b-diketiminato stabilised aluminium hydride complex is an excellent catalyst for hydroboration of alkynes and carbonyl groups. [5] More recently, Cowley, Thomas and Bismuto revealed that DIBAL(H), and Et 3 Al·DABCO can catalyse hydroboration of alkynes. [6] Our groups interests lie in exploiting the synergistic reactivity imparted by two distinct metal centres [7,8] installed within a bimetallic complex.…”