New stable cyclopentadienyl iron(II) complexes containing 3,5-dimethylpyrazolyl phosphine: X-ray structure of [FeCp(CO)2PPh2(Me2Pz)]BF4

Very stable complexes of general formula [FeCp(CO)xPh2P(Me2Pz)]BF4, where x=1(1)–2(2) were prepared by room temperature reaction of the 3,5-dimethylpyrazolylphosphine ligand with [Fe2(CO)2(C5H5)2]. When [FeCp(CO)2Ph2P(Me2Pz)]BF4 (1) was treated with (CH3)3NO·2H2O, one coordinated CO was lost and complex 2 was formed. 1H-, 13C- and 31P-NMR spectra supported a structure of 2 with pyrazolyl ligand chelated to iron forming a four-membered metallocycle.