iodine in tetrahydrofuran (N2), I2 added slowly to Co2(CO)8 in THF, stirred at 25°C for 3 h, (C5H4Br)Tl added, stirred for 20 h; filtered, solvent removed in vacuo, mixed with alumina in Et2O, solvent removed, chromd. on alumina with pentane, solvent removed, recrystn. (twice from pentane at -78°C) and molecular destillation (25°C/E-3 Torr) possible, elem. anal.;

in benzene (N2), stirred at reflux for 24 h; cooled, filtered, solvent removed in vacuum (recrystn. from MeOH possible);