Structural variations in nickel, palladium, and platinum complexes containing pyrimidyl N-heterocyclic carbene ligand

Nickel(II), palladium(II), and platinum(II) complexes of 2-(3-mesitylimidazolylidenyl)pyrimidine (L), [Ni2(μ-Cl)2(L)4][Ag2Cl4] (3), [Ni2(μ-I)2(L)4][NiI(L)2(CH3CN)]2[Ag4I8] (4), [PdCl2(L)] (5), [PdI2(L)] (6), and [PtCl(L)2][AgCl2] (7) have been obtained from the carbene transfer reactions of [Ag(L)Cl] (2). These complexes have been fully characterized by spectroscopic methods and single-crystal X-ray structure analyses. The mono(carbene)palladium and bis(carbene)platinum complexes display normal square–planar structures. Nickel complexes 3 and 4 are rare examples of paramagnetic nickel(II) complexes of N-heterocyclic carbenes having octahedral geometry.