Mono- and dinuclear tetraphosphabutadiene ferrate anions.

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