in tetrahydrofuran all manipulations under dry N2; adding dropwise 5,5,10,10-tetrachlorotricyclo(7.1.0.0(4.6))decane to suspn. of Na2Fe(CO)4 (-40°C), removing solvent after 2.5 h (vacuum); extg. (petroleum ether, 40 - 60°C), filtering (kieselguhr), removing solvent, chromy. (silica gel, petroleum ether, 40 - 60°C), eluting light brown band (desired complex) and green band (Fe3(CO)12);