X-ray photoelectron spectral study of the planar NiS<sub>4</sub>, NiS<sub>2</sub>PCl and NiS<sub>2</sub>P<sub>2</sub> chromophores and X-ray crystal structure of piperidinedithiocarbamatobis(triphenylphosphine) nickel(II) perchlorate triphenylphosphine monohydrate