2-Phenoxy-1,3,2-diazaphospha-[3]ferrocenophane and related derivatives (oxide, sulfide, selenide) were prepared, characterized in solution by multinuclear magnetic resonance methods (1D and 2D 1H, 13C, 15N and 31P NMR) and in the solid state by X-ray structural analysis. The conformation of the 2-phenoxy derivative differs from that of the 2-tert-butyl compound. For further comparison, 2-R- 2,3-dihydro-1H-1,3,2-diazaphospha-phenalene derivatives R = 'Bu, PhO were prepared and studied by the same NMR techniques. The molecular structure of a selenide was determined, and together with the NMR evidence, it was concluded that the conformation of these heterocycles is independent of the respective substituent at the phosphorus atom
