Electrochemical (polarographic, cyclic voltammetric, and coulometric) and coordination behaviour of several symmetrically and unsymmetrically substituted phosphiniminocyclotrithiazenes have been studied. Polarograms of R3PN-S3N3 R = C6H5, p-ClC6H4, p-H3CC6H4, and (OC4H8N)), Ph2OC4H8N)PN-S3N3, and Ph(OC4H8N)2PN-S3N3 give two cathodic waves. Cyclic voltammograms of Ph3PN-S3N3 (1) and (OC4H8N)3PN-S3N3 (2) reveal nearly the same oxidation peak potential but different reduction potentials. Controlled potential electrolysis of 1 and 2 at +0.6 V indicates exocyclic cleavage and ring degradation. Cathodic reduction behaviour of Ph3PN-S3N3 suggests the possibility for the) formation of 1,5-(Ph)3(PN)2S4N4 under electrochemical conditions. Reaction of nickel chloride hexahydrate with heterocycle 1 in 1:2 molar ratio in acetonitrile affords the complex, ([NiS2N2H2] (A) (90% yield) and [Ph3PNH2]Cl salt as products. Analogous reactions with other ligands of this type (two symmetrical (sym.) and three unsymmetrical (unsym.)) except 2 also give A, while ligand 2 reacts with anhyd NiCl2 in an equimolar ratio to afford a dark green, square-planar complex ((OC4H8N)3(PN-S3(N·NiCl 2 (B)) whose ESCA results assist in providing its coordination details. The study reveals a high tendency of these heterocycles to different types of ring cleavage.