New aspects of the chemistry of the phosphoranimine Cl(3)P=NMes* (Mes* = 2,4,6-tri-tert-butylphenyl) (7) and the phosphinimine ClP=NMes* (2) have been explored. A cationic derivative of 7 was prepared from the reaction between this species and DMAP (DMAP = 4-dimethylaminopyridine) in the presence of the halide abstraction agent AgOTf (OTf = OSO(3)CF(3)) which yielded the donor-stabilized cation [DMAP-PCl(2)=NMes*](+) ([9](+)). When treated with tertiary phosphines (n)Bu(3)P or Ph(3)P, 7 was found to undergo a reductive dechlorination reaction to yield 2 and dichlorophosphoranes R(3)PCl(2) (R = (n)Bu (13a), Ph (13b)). The phosphinimine 2 reacts with Cl(-) sources to form the novel dichlorophosphinamide anion [Cl(2)PNMes*](-) ([14](-)) which was characterized in solution. Treatment of [Ph(4)P][14], generated in situ, with GaCl(3) or MeOTf regenerated 2 and provided further evidence for the formation of the anion [14](-). In addition, phosphoranimine 2 was found to undergo an unexpected oxidative cyclization reaction when treated with the oxygen transfer agent pyridine-N-oxide to yield a P-chlorophosphoryl-ox-3-azoline (18).