Synthesis, spectroscopic properties, and crystal structure of 2,2'-bipyridyldimesitylnickel(II)

The dimesitylnickel(II) complex [(bpy)NiMes(2)] (Mes = mesityl = 2,4,6-trimethylphenyl) was prepared and examined spectroscopically and electrochemically. The crystal and molecular structure was determined from single crystal X-Ray diffraction experiments (monoclinic, P2(1)/n, Z = 4, a = 8.3092(8) (A) over dot, b = 18.233(2) (A)over dot, c = 15.226(2) (A)over dot, beta= 98.035(6)degrees). The nickel atom displays a distorted square pla nar environment. The axial positions of the square plane are shielded by each one of the methyl groups on the mesityl substituents. The complex shows electrochemical reduction processes that are mainly centered on the bpy ligand as inferred from spectroelectrochemical investigations (EPR and UV/Vis/NIR absorption) of the radical anion or dianion. The observed oxidation is assigned to a Ni-II/Ni-III couple. The title complex exhibits strongly solvatochromic long-wavelength electronic absorptions.