Unusual reactivity in organoaluminium and NHC chemistry: deprotonation of AlMe3 by an NHC moiety involving the formation of a sterically bulky NHC–AlMe3 Lewis adduct

Abstract

A sterically congested NHC-AlMe(3) Lewis adduct (NHC = 1,3-di-tert-butylimidazol-2-ylidene) was found to either isomerize to an "abnormal" NHC-AlMe(3) species or to be involved in the deprotonation of AlMe(3) to form the corresponding imidazolium species along with an AlMe(3)-stabilized methylene aluminium anion.

Coordination chemistry of ditopic carbanionic N-heterocyclic carbenes

“…The availability of the free carbene to do further chemistry was demonstrated by the reaction of the complexes with various Lewis acids such as BH 3 , AlMe 3 and CO 2 (Fig. 20), in a similar manner to the Lewis acid-base adducts which are already known for free NHCs [95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112]. …”

Oxidative Cleavage of C=S and P=S Bonds at an AlI Center: Preparation of Terminally Bound Aluminum Sulfides

“…Thec losest relative of compound 5 is the deprotonated alumothiol [NacNacAl(S)X] À reported by Roesky et al [32] Four derivatives of this anion differing in the identity of the countercation and the nature of the Xg roup (X = SH or OP(OEt) 2 )have been structurally characterized, with the Al-Sd istances falling in the range of 2.115-2.124 .A nother closely related compound, also reported by the Roesky group, is the NHC-stabilized aluminum hydride complex 6 with ad eprotonated NacNac ligand. However,t his parameter falls within aw ide range of lengths (2.008-2.162 )w ith only four structures containing longer Al-C distances (ranging from 2.118(2) [35] to 2.162(2) [36] ). As imilar coordination mode was observed by Driess and co-workers for the NHC-stabilized silanone compound 7 featuring aS i =Od ouble bond.…”

Sterically Bulky NHC Adducts of GaMe3 and InMe3 for H2 Activation and Lactide Polymerization

“…While stable for days in benzene/toluene at room temperature (under inert atmosphere), they quickly decompose to unknown species in CH2Cl2 and THF at room temperature, in line with severely hindered Lewis pairs. The NMR data for 3 and 4 only display sharp resonances As earlier mentioned, the sterically hindered Lewis pairs (ItBu)MMe 3 (M = Ga, In) are unstable and rearrange to the corresponding C4-bonded isomers (aItBu)MMe 3 (Scheme 1) [12][13][14]. To avoid such isomerization, the backbone-saturated carbene StBu, prepared according to a known procedure [23], was coordinated to GaMe 3 and InMe 3 .…”

“…As earlier mentioned, the sterically hindered Lewis pairs (ItBu)MMe3 (M = Ga, In) are unstable and rearrange to the corresponding C4-bonded isomers (aItBu)MMe3 (Scheme 1) [12][13][14]. To avoid such isomerization, the backbone-saturated carbene StBu, prepared according to a known procedure [23], was coordinated to GaMe3 and InMe3.…”

“…FLP reactivity has attracted tremendous attention over the past few years thanks to the ability of sterically hindered Lewis pairs and FLPs to activate numerous polar/unsaturated substrates, including H 2 and CO 2 [9][10][11]. In the area of group 13 metal species, we and others have shown that sterically bulky group 13 metal Lewis adducts may display limited stability and readily isomerize to their "abnormal" counterparts for steric relief of (NHC)MMe 3 (Scheme 1, taking the example of adducts (ItBu)MMe 3 ) [12][13][14].…”