PENTACARBONYLS OF RUTHENIUM AND OSMIUM .4. SYNTHESIS OF ALKYL- AND ACETYLOSMIUM CARBONYLS

The sodium salt Na[OsH(CO)4] has been obtained in high yields by the reduction of OsH2(CO)4 with sodium sand in tetrahydrofuran. The nuclear magnetic resonance and infrared spectra are in agreement with a symmetry C3v and a metal-hydrogen bond. No evidences for the formation of the dianion Os(CO)42- were obtained. The monosodium derivative is a strong nucleophilic reagent and reacts with methyl halides to give the new alkyl compounds OsCH3H(CO)4, OsCH3- I(CO)4, and Os(CH3)2(CO)4. Nmr and infrared spectra indicate a cis-octahedral structure for all three substances. Methylhydridotetracarbonylosmium could not be isolated in a pure state; at room temperature it decomposes very rapidly with evolution of methane. On addition of triphenylphosphine, the decomposition is promoted; Os(CO)4P(C6H5)3 and Os(CO)3(P(C6Hs)3)2 are formed, together with some monosubstituted OsCH3H(CO)3P(C6H5)3. The two other alkyl derivatives OsCH3I(CO)4 and Os(CH3)2(CO)4 seem to be thermally very stable. The reaction of OsBr2(CO)4 with methylmagnesium bromide was also investigated. The salt [MgBr]2[Os(COCH3)2Br2(CO)2].5THF was obtained. Infrared and nmr data suggest an all-cis configuration for the anion Os(COCH3)2Br2(CO)22-. © 1969, American Chemical Society. All rights reserved.