Mixed Azido-N-Heterocyclic Carbene Complexes of Nickel(II) as a Template for New Organometallics Bearing Carbodiimido, Tetrazolato, and Abnormal Tetrazolin-5-ylidene Ligands

Salt 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 diazidobis(carbene) complex trans-[Ni(N-3)(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) at 70 degrees 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-Bu-t,Me)(2)(NHC)(2)] (BF4)(2) (7, Bu-t = 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 center dot 2CH(2)O(2) have also been confirmed by X-ray diffraction studies.