The N-phosphorylated thiourea PhNHC(S)NHP(O)(OPh)(2) (HL) was synthesized by the reaction of PhNH2 and (PhO)(2)P(O)NCS. Reaction of the KL salt, generated in situ, with NiCl2 leads to pale violet [NiL2] with a 1,3-N,S- coordination mode of the ligands. Interaction of [NiL2] with pyrazine (pz) yields the 1:1 coordination polymer [NiL(2)pz](n). An unexpected change in the coordination mode of the phosphorus-containing ligands L from 1,3-N,S- to 1,5-O,S- was found in [NiL(2)pz](n) upon coordination of additional donor ligands. [NiL(2)pz](n) dissolved in tri-n-octylphosphine (TOP) was decomposed in hot hexadecylamine to give capped face-centered cubic Ni nanoparticles with an average particle size of 17(2) nm.