First structural characterisation of penta- and hexa-phosphorus analogues of ferrocene. Synthesis, crystal and molecular structure of the air-stable, sublimable iron sandwich compounds [Fe(η 5 -C 2 R 2 P 3 ) 2 ], and [Fe(η 5 -C 3 R 3 P 2 )(η 5 -C 2 R 2 P 3 )](R = Bu t )

The first structurally characterised penta- and hexa-phosphorus analogues of ferrocene, bis-(η5–2,5-di-t-butyl-1,3,4-triphosphacyclopentadienyl)iron and (η5-2,4,5-tri-t-butyl-1,3-diphosphacyclopentadienyl)-(η5-2,5-di-t-butyl-1,3,4-triphosphacyclopentadienyl)iron, are described.