in diethyl ether reaction of C4H9Li (1.2 equiv.) and Br(C5H4)Fe(C5H5) to Li(C5H4)Fe(C5H5) in diethyl ether, warmed up to room temp., stirred 45min, recooled to -78°C, dropwise addn. of (NPF2)3 in diethyl ether, stirred, 6h, room temp., solvent removed, under N2; chromy. (hexane (Fe(C5H5)2) - dichloromethane/hexane(1:5) (N3P3F5(C5H4)Fe(C5H5)), elem. anal. - dichloromethane/hexane(1:1) (N3P3F4((C5H4)Fe(C5H5))2));