Mono- and dinuclear tetraphosphabutadiene ferrate anions

Reduction of [(CpFe)-Fe-Ar(-Br)](2) (1, Cp-Ar = C-5(C6H4-4-Et)(5)) by potassium napthalenide, followed by the addition of white phosphorus, affords [K(18-c-6){(CpFe)-Fe-Ar((4)-P-4)}] (2, 18-c-6 = [18]crown-6), which features a planar cyclo-P-4(2-) ligand. The related diiron complex [Na-2(THF)(5)((CpFe)-Fe-Ar)(2)(,(4:4)-P-4)] (3) was obtained by reducing 1 with sodium amalgam in the presence of P-4. Protonation of 3 affords [Na(THF)(3)][((CpFe)-Fe-Ar)(2)(,(4:4)-P-4)(H)] (4), while the reaction of 3 with trimethylchlorosilane gives the nortricyclane compound P-7(SiMe3)(3) as the main product.