Iron- and Ruthenium-Linked Phosphazenes¹

A series of new organometallic phosphazenes that contains Fe-P, Ru-P, Ru-Ru, and Fe-Ru bonds has been isolated. The anions [Fe(CO)₂Cp]^- and [Ru(CO)₂Cp]^- react with (NPF₂)₃ (2) to replace first one and then two (geminal) fluorine atoms by M(CO)₂Cp groups. The monoruthenium derivative (5) reacts with [Fe(CO)₂Cp]^- to form a geminal, mixed-metal organometallic phosphazene (7) that, on photolysis, undergoes decarbonylation to an Fe-Ru bonded derivative (8). The monoiron cyclotriphosphazene (9) does not yield the same mixed-metal species when treated with [Ru(CO)₂Cp]^- but instead forms the new mixed-metal dimer, FeRu(CO)₄Cp₂ (10). This dimer can also be prepared by the reaction of [Ru(CO)₂Cp]^- with Fe(CO)₂CpI. Species 8 and its diiron analogue, 4, undergo metal-metal bond cleavage with carbon monoxide. Species 7 and 8 are the first examples of phosphazenes with two different metals linked to a phosphazene ring. The new compounds were characterized by ³¹P, ¹⁹F, and ¹H NMR, infrared, and mass spectral techniques. In addition, an X-ray crystal structure analysis of the mixed-metal phosphazene 8 was carried out. The Fe-Ru bond distance in 8 is 2.698 (1) Á and the Fe-P-Ru bond angle is 73.93 (2)°. Evidence was obtained that the organometallic unit perturbs the structure of the phosphazene ring.