Mixed azido-N-heterocyclic carbene complexes of nickel(II) as a template for new organometallics bearing carbodiimido, tetrazolato, and abnormal tetrazolin-5-ylidene ligands

Abstract

metathesis reaction of the dihalo-bis(carbene) complex trans-[NiBr2(NHC)2] (1, NHC = 1,3- diisopropylbenzimidazolin-2-ylidene) with NaN3 in DMF at elevated temperature afforded the diazido- bis(carbene) complex trans-[Ni(N3)2(NHC)2](2) as a red crystalline solid in a yield of 78%. Complex 2 served as a metal-template for the 1,3-dipolar cycloaddition of 2,6-dimethylphenylisocyanide (CN-Xyl) to the azido ligands to yield the mixed tetrazolato-carbodiimido complex trans-[Ni(CN4-Xyl)(NCN- Xyl)(NHC)2](3) at ambient temperature and the dicarbodiimido complex trans-[Ni(NCN-Xyl)2(NHC)2] (4)at70 °C. Reaction of alkyl isocyanides with 2 at ambient temperature gave the ditetrazolato complexes trans-[Ni(CN4-R)2(NHC)2](5,R = tert-butyl; 6,R = cyclohexyl) in good yields. The novel cationic "abnormal" tetrazolin-5-ylidene complex trans-[Ni(CN4-tBu,Me)2(NHC)2](BF4)2 (7, tBu = tert-butyl) was synthesized by direct methylation of 5 with [Me3O]BF4. All compounds have been fully characterized by multinuclear NMR spectroscopies and ESI mass spectrometry. The solid state molecular structures of complexes 2, 4, 5, and 7 · 2CH2Cl2 have also been confirmed by X-ray diffraction studies. © 2009 American Chemical Society.