in xylene reflux (stirring, 8 h), concn. (vacuum); chromy. (Al2O3, pentane, pentane/toluene 1/1), recrystn. (pentane, ca.-18°C);

in toluene inert gas; THF added to mixt. of solid Fe compd. (0.254 mmol) and Rh compd (0.262 mmol), stirred for 4 d at room temp.; concd., dried, dissolved CH2Cl2, chromd. (SiO2, hexane/toluene), recrystd. (toluene/hexane);

in n-heptane a mixt. of (C6Me6)Ru(C2H4)2 and an excess of (C5Me5)Rh(CO)2 was refluxed in heptane for 4 h under N2;; after evapd. in vacuo, the residue was subjected to column chromy. on SiO2 at -35°C; elem. anal. for the tetranuclear cluster;;

in nitromethane-d3=CD3NO2 N2-atmosphere; equimolar amts., room temp.; not isolated, detected by (31)P-NMR spectroscopy;