Mössbauer and preparative studies of some iron(II) complexes of diphosphines

Analytical and Mössbauer spectral data show that Ph2PCH2CH2PPh2(dppe) forms adducts [FeCl2(dppe)] and [FeI2(dppe)], and that [FeCl2(dppe)2] does not exist. The phosphine 1,2-C6H4(PPh2)2(opdp) forms adducts FeX2(opdp)2, which exists in one form (high-spin, trans octahedral) for X = Cl, and in two isomeric forms for X = Br or I. One isomer for X = I is high-spin, trans octahedral, and the other is ionic low-spin, and five-co-ordinate. A comparison is made of these structures and of their Mössbauer spectra with those of derivatives of Me2PCH2CH2PMe2, Et2PCH2CH2PEt2, Pri2PCH2CH2Pri2, and Ph2PCH2PPh2.