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

Abstract

Abstract 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 SbCl 2 R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me 2 Im Me (1,3,4,5‐tetra‐methyl‐imidazolin‐2‐ylidene), i Pr 2 Im Me (1,3‐di‐ iso propyl‐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‐ iso propylphenyl) and c AAC Me with antimony(III) compounds SbCl 2 R (R=Cl ( 1 ), Ph ( 2 ) and Mes ( 3 )) yields the adducts NHC ⋅ SbCl 2 R (R=Cl ( 4 ), Ph ( 5 ) and Mes ( 6 ); NHC=Me 2 Im Me ( a ), i Pr 2 Im Me ( b ), Dipp 2 Im ( c ) and Mes 2 Im ( d )) and cAAC Me ⋅ SbCl 2 R (R=Cl ( 4 e ) and Ph ( 5 e )). Thermal treatment of (Dipp 2 Im) ⋅ SbCl 2 Ar (Ar=Ph ( 5 c ) and Mes ( 6 c )) in benzene leads to isomerization to the backbone coordinated a NHC‐adduct a Dipp 2 Im ⋅ SbCl 2 Ar (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 GaCl 3 or Ag[BF 4 ] to obtain the imidazolium salts [ a Dipp 2 Im ⋅ SbClMes][BF 4 ] ( 9 ) and [ a Dipp 2 Im ⋅ SbClMes][GaCl 4 ] ( 10 ).