The reaction of Fe₃(CO)₁₂ with cis-2,4-di(tert-butylamino)-1,3-di(tert-butyl)-1,3,2,4-cyclodiphosph-azane (L), yielded two novel mononuclear carbonyl iron derivativescontaining cyclodiphosphazane ligand, Fe(CO)₄[｛P(NHBu-t)NBu-t｝₂] (1) and Fe(CO)₄[P(NHBu-t) (NBu-t)₂P(O)H] (2). These compounds were characterized by elemental analysis, IR and ¹H NMR spectra, and the structures of 1 and 2were determined by single-crystal X-ray diffraction. 1: orthorhombic, Pna2(1), a=1.7038(9) nm, b=0.8856(5) nm, c=3.5659(18)nm, V=5.381(5) nm³, D_c=1.275 g/cm³, Z=8. 2:monoclinic, P2(1)/n, a=0.9999(2) nm, b=1.4476(3) nm, c=1.5559(3) nm, β=92.40(3)°, V=2.2504(8) nm³, D_c=1.361 g/cm³, Z=4. In the two carbonyl iron derivatives, the phosphorus-nitrogen heterocycles were not cleaved during the reaction, and one P atom of them was coordinated to Featom. In the compound 2, another P(III) atom was oxidized to the P(V), phosphonic amide P(O)H, in which the bond between P and NHBu-t group was cleaved and one P—H bond was formed.

Key words: carbonyl iron derivative, cyclophosphazaneligand, synthesis, crystal structure