CH/π interaction in nickel(II) complexes derived from 2-substituted benzothiazolines

By reaction of 2-(3,5-di-tert-butyl-4-hydoxyphenyl)benzothiazoline with nickel(II) acetate tetrahydrate, the complex bis[2-(3,5-di-tert-butyl-4-hydroxyphenylmethyleneamino)benzenethiolato]nickel(II) 1 has been prepared. Its crystal structure has been elucidated, showing an intramolecular approach of the tert-butyl group to the aromatic ring of the 2-aminobenzenethiol moiety. In addition, variable-temperature H-1 NMR studies of 1 indicated the restriction of rotation of the pendant arm. Such behaviour is attributed to the existence of a CH/pi interaction between the tert-butyl group and the aromatic ring of another ligand. To provide further evidence for the CH/pi interaction in nickel(II) complexes derived from 2-substituted benzothiazolines, we have also prepared a pair of nickel(II) complexes (2 and 3) with meta-substituted phenyl groups as pendant arms. A comparison between 2 with a methyl group and 3 with a chlorine atom on the pendant arm provided insight into the CH/pi interaction that controls the orientation of the pendant arm.