N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Adducts of Antimony(III)

A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAAC(Me) (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with antimony(III) chlorides of the general formula SbCl2R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me(2)Im(Me) (1,3,4,5-tetra-methyl-imidazolin-2-ylidene), iPr(2)Im(Me) (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Mes(2)Im, Dipp(2)Im (R(2)Im=1,3-di-organyl-imidazolin-2-ylidene; Mes=2,4,6-trimethylphenyl, Dipp=2,6-di-isopropylphenyl) and cAAC(Me) with antimony(III) compounds SbCl2R (R=Cl (1), Ph (2) and Mes (3)) yields the adducts NHC SbCl2R (R=Cl (4), Ph (5) and Mes (6); NHC=Me(2)Im(Me) (a), iPr(2)Im(Me) (b), Dipp(2)Im (c) and Mes(2)Im (d)) and cAAC(Me) SbCl2R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp(2)Im) SbCl2Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated (NHC)-N-a-adduct (a)Dipp(2)Im SbCl2Ar (Ar=Mes (7) and Ph (8)) ((a) denotes abnormal coordination mode of the NHC) in high yields. One of the chloride substituents at antimony of 7 can be abstracted by GaCl3 or Ag[BF4] to obtain the imidazolium salts [(a)Dipp(2)Im SbClMes][BF4] (9) and [(a)Dipp(2)Im SbClMes][GaCl4] (10).

Automated summary

A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes and cyclic (alkyl)(amino)carbene with antimony(III) chlorides was conducted, revealing a series of products formation and thermal isomerization reactions.