Highly regioselective homocoupling of N,N-dialkylanilines can be achieved in water with cerium reagents, in which various N,N,N′,N′-tetraalkylbenzidines are obtained from N,N-dialkylanilines either by direct oxidation by cerium（Ⅳ）reagents or by cerium（Ⅲ） reagents in the presence of hydroperoxide.
The crystal of the title compound, [Ni（C15HgBr2ClNO2）（C18H15P）（C10H7）]（C18H15P）, has been prepared and confirmed by X-ray diffraction. The crystal belongs to the triclinic system, space group PI with a = 9.991（3）, b = 15.250（4）, c = 18.542（5） A, α = 104.927（5）, β = 104.009（6）, γ = 94.422（6）°, V= 2619.2（11）A^3, Z = 2, Mr = 1140.91, Dc= 1.447 g/cm^3, F（000） = 1160 and μ（MoKα） = 2.053 mm^-1. The structure is refined to R = 0.0779 for 3773 observed reflections with I 〉 2σ（I） and wR = 0.1694 for 9026 unique reflections. The crystal （1-PPh3） is composed of neutral nickel（Ⅱ） complexes and co-crystallized PPh3 molecules. Intramolecular C-H...π interactions between C-H bond of the aldehyde group and phenyl ring of the coordinated PPh3 molecule in the nickel（Ⅱ） complex are observed, and intermolecular π-π interactions between neutral nickel（Ⅱ） complexes are also found in the crystal.
