胺稳定的铝烷(NMe3)*AlH3.1与主链饱和的N-杂环碳烯(NHC)SIDiPp(SIDiPp=1,3-双-{2,6-二-异丙基-苯基}-咪唑烷-2-亚基)在0°C下的反应产生了NHC铝烷加合物(SIDiPpp)*AlH3.2。在升高的温度下反应或在室温下延长的反应产生NHC的环膨胀反应(RER)的产物,3*(NMe3)。后者与空间位阻较小的NHC(IMeMe{=1,3,4,5-四甲基-咪唑啉-2-亚基},IiPrMe{=1,3-二异丙基-4,5-二甲基-咪唑啉-2-亚基},和IiPr{=1,3-二-异丙基-咪唑啉-2-亚基})提供了NHC稳定的RER产品(NHC)·AlH(RER-SIDippH2)3·(NHC)(NHC=IMeMe,IiPrMe,IiPr),虽然在空间上要求更高的NHCIDipp(=1,3-双-{2,6-二-异丙基-苯基}-咪唑啉-2-亚基)中未观察到反应,SIDipp和ItBu(=1,3-二叔丁基-咪唑啉-2-亚基)。在室温下,从(SIDipp)‧AlH3.2和NHC开始也获得了化合物3‧(NHC)。将(SIDipp)*AlH3.2的溶液加热至95°C,导致NHC脱碳,并在乙烯损失的情况下用氢化铝取代卡宾碳原子。随后二聚得到顺式-[AlH{m-N(Dipp)CH2CH2N(Dipp)}]2.4二聚物。NHC连接的烷基铝(SIDpp)的加热溶液AlR3.2R(R=Me,Et)到145°C反而导致NHC主链完全断裂,产生乙烯和二烷基铝(III)脒酯{DippNC(R)NDipp}AlR2.5R(R=Me,Et)。
The reaction of the amine-stabilized alane (NMe3) ⋅ AlH3 1 with the backbone-saturated N-heterocyclic carbene (NHC) SIDipp (SIDipp=1,3-bis-{2,6-di-iso-propyl-phenyl}-imidazolidin-2-ylidene) at 0 °C yielded the NHC alane adduct (SIDipp) ⋅ AlH3 2. Reaction at elevated temperatures or prolonged reaction at room temperature gave the product of a ring expansion reaction (RER) of the NHC, (NMe3) ⋅ AlH(RER-SIDippH2) 3 ⋅ (NMe3). Subsequent reaction of the latter with sterically less hindered NHCs (IMeMe {=1,3,4,5-tetramethyl-imidazolin-2-ylidene}, IiPrMe {=1,3-di-iso-propyl-4,5-dimethyl-imidazolin-2-ylidene}, and IiPr {=1,3-di-iso-propyl-imidazolin-2-ylidene}) afforded the NHC-stabilized RER-products (NHC) ⋅ AlH(RER-SIDippH2) 3 ⋅ (NHC) (NHC=IMeMe, IiPrMe, IiPr), while no reaction was observed with the sterically more demanding NHCs IDipp (=1,3-bis-{2,6-di-iso-propyl-phenyl}-imidazolin-2-ylidene), SIDipp and ItBu (=1,3-di-tert-butyl-imidazolin-2-ylidene). The compounds 3 ⋅ (NHC) were also obtained starting from (SIDipp) ⋅ AlH3 2 and NHC at room temperature. Heating solutions of (SIDipp) ⋅ AlH3 2 without additional base to 95 °C resulted in decarbonization of the NHC and substitution of the carbene carbon atom with aluminum hydride under loss of ethene. Subsequent dimerization afforded cis-[AlH{μ-N(Dipp)CH2CH2N(Dipp)}]2 4_dimer. Heating solutions of the NHC-ligated aluminum alkyls (SIDipp) ⋅ AlR3 2R (R=Me, Et) to 145 °C instead led to complete scission of the NHC backbone with evolution of ethene and isolation of the dialkylaluminium(III) amidinates {DippNC(R)NDipp}AlR2 5R (R=Me, Et).