Carbonylation of ruthenium trichloride in methanol affords white dimeric [Ru(CO)3Cl2]2and Ru3(CO)12. Crystallisation of the carbonyl chloride from tetrahydrofuran gives the complex C4H8O,Ru(CO)3Cl2, while sublimation yields a yellow isomeri carbonyl chloride. Treatment of the tetrahydrofuran adduct with donor ligands leads to evolution of CO and precipitation of complexes of the type L2Ru(CO)2Cl2. The carbonyl Ru3(CO)12 is obtained in high yield by carbonylating ruthenium trichloride in methanol at CO pressures of up to 10 atm., with zinc as a halogen acceptor.