[Ni(<i>i</i>Pr₂Im)₂Br₂]: A Convenient Entry into NHC Nickel Chemistry

Abstract The reaction of the NHC i Pr 2 Im [NHC=N‐heterocyclic carbene, i Pr 2 Im = 1, 3‐bis( iso propyl)imidazolin‐2‐ylidene] with freshly prepared NiBr 2 in thf or dme results in the formation of the air stable nickel(II) complex trans ‐[Ni( i Pr 2 Im) 2 Br 2 ] ( 2 ). Complex 2 was structurally characterized. Thermal analysis (DTA/TG) reveals a very high decomposition temperature of 298 °C. Reduction of 2 with sodium or C 8 K in the presence of the olefins COD (cyclooctadiene) or COE (cyclooctene) affords the highly reactive compounds [Ni 2 ( i Pr 2 Im) 4 (COD)] ( 1 ) and [Ni( i Pr 2 Im) 2 (COE)] ( 4 ). Alkylation of 2 with organolithiums leads to the formation of trans ‐[Ni( i Pr 2 Im) 2 ( R ) 2 ] [ R = Me ( 5 ), CH 2 SiMe 3 ( 6 )], whereas the reaction of 2 with LiCp* [Cp* = (η 5 ‐C 5 (CH 3 ) 5 )] at 80 °C causes the loss of one NHC ligand and affords [(η 5 ‐C 5 (CH 3 ) 5 )Ni( i Pr 2 Im)Br] ( 7 ).