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

Abstract

AbstractA systematic study on Lewis‐acid/base adducts of N‐heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAACMe (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 Me2ImMe (1,3,4,5‐tetra‐methyl‐imidazolin‐2‐ylidene), iPr2ImMe (1,3‐di‐isopropyl‐4,5‐dimethyl‐imidazolin‐2‐ylidene), Mes2Im, Dipp2Im (R2Im=1,3‐di‐organyl‐imidazolin‐2‐ylidene; Mes=2,4,6‐trimethylphenyl, Dipp=2,6‐di‐isopropylphenyl) and cAACMe 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=Me2ImMe (a), iPr2ImMe (b), Dipp2Im (c) and Mes2Im (d)) and cAACMe ⋅ SbCl2R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp2Im) ⋅ SbCl2Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated aNHC‐adduct aDipp2Im ⋅ 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 [aDipp2Im ⋅ SbClMes][BF4] (9) and [aDipp2Im ⋅ SbClMes][GaCl4] (10).