Reaction of the Re1" bis-diazenido starting materials [ReCI(NNC,H4X-4),(PPh3),] (X = CI 1 or Me 2) with excess dppe (Ph,PCH,CH,PPh,) in methanol-toluene under reflux gave the novel orange-brown, formally 20-electron Re"' bis-diazenido cations [Re(NNC,H4X-4),(dppe),] + (X = CI or Me) in good yield by addition of a suitable anion to the cooled reaction mixture. Reaction of 1 and 2 with the more reducing dmpe (Me,PCH,CH,PMe,) ligand gave the formally 20-electron bis-diazenido cation [Re(NNC,H4X-4),(dmpe),] + for X = CI but the 18-electron mono-diazenido cation [ReCI(NNC,H,X-4)(dmpe),] + for X = Me. The structures of complexes [Re(NNC,H4Me-4),(dppe),] [PF,]-2dmf (dmf = dimethylformamide) 5, [Re(NNC,H4CI-4),(dmpe),] [PF,] 6 and [ReCI(NNC,H,Me-4) (dmpe),] [PF,] 7 have been determined: 5, triclinic, space group PT, a = 13.046(3), b =13.250(3), c = 12.233(4) A. a = 11 0.74(2), p = 95.86(2), y = 11 5.83(2)", Z = 1, R = 0.040; 6 monoclinic, space group P2,/c, a = 8.992(2), b = 21.947(2), c = 18.982(2) A, p =91.45(1)", Z = 4, R = 0.056; 7 orthorhombic, space group Pnma, a = 19.298(2), b = 11.327(2), c = 13.960(2) A, = p = y = 90". Z = 4, R = 0.042. All