The reactivity of an anionic phosphanylphosphinidene complex of tungsten(VI), [(2,6-i-Pr2C6H3N)(2)(Cl)-W(eta(2)-t-Bu2P=P)]Li.3DME toward PMe3, halogenophosphines, and iodine was investigated. Reaction of the starting complex with Me3P led to formation of a new neutral phosphanylphosphinidene complex, [(2,6-i-Pr2C6H3N)(2)(Me3P)W(eta(2)-t-Bu2P=P)]. Reactions with halogenophosphines yielded new catena-phosphorus complexes. From reaction with Ph2PCl and Ph2PBr, a complex with an anionic triphosphorus ligand t-Bu2P-P(-)-PPh2 was isolated. The main product of reaction with PhPCl2 was a tungsten(VI) complex with a pentaphosphorus ligand, t-Bu2P-P(-)P(Ph)-P(-)P-t-Bu-2. Iodine reacted with the starting complex as an electrophile under splitting of the P-P bond in the t-Bu2P=P unit to yield [(1,2-eta-t-Bu2P-P-P-t-Bu-2)W(2,6-i-Pr2C6H3N)(2)Cl], t-Bu2PI, and phosphorus polymers. The molecular structures of the isolated products in the solid state and in solution were established by single crystal X-ray diffraction and NMR spectroscopy.