Le diméthyl‐ et le diéthyl‐tétracarbonylosmium Synthèse et réactivité

Abstract

Abstract The sodium salt Na 2 [Os(CO) 4 ] has been obtained in high yields by the reduction of either OsH 2 (CO) 4 or Os 3 (CO) 12 with sodium sand in the presence of catalytic amounts of 2, 2′‐bipyridyle. The reaction of Na 2 [Os(CO) 4 ] with alkylating agents such as methyl and ethyl iodide produces OsR 2 (CO) 4 (R = CH 3 , C 2 H 5 ). NMR. and IR. spectra indicate a cis ‐octahedral structure of symmetry C 2 v for these new alkyl compounds. Bromine breaks one osmium‐carbon bond in cis ‐Os(CH 3 ) 2 (CO) 4 to give cis ‐OsCH 3 Br(CO) 4 , whereas in cis ‐Os(C 2 H 5 ) 2 (CO) 4 both ethyl groups are easily displaced by bromine to give cis ‐OsBr 2 (CO) 4 . Under CO pressure and at elevated temperature cis ‐Os(CH 3 ) 2 (CO) 4 is converted to Os(CO) 5 and ethane. With cis ‐Os(C 2 H 5 ) 2 (CO) 4 two CO are inserted in osmium‐carbon bonds to give . NMR. and IR. data suggest a cis ‐configuration for this derivative and the possibility of the presence of rotational isomers.