Two new selective C-C bond formation procedures are described; the Cu-catalyzed alkylation of organomanganese chlorides by alkyl halides and the Fe-catalyzed alkenylation of organomanganese chlorides by alkenyl halides. These reactions have a large scope and give high yields under mild conditions (rt, 1 h). They are highly chemoselective and allow the preparation of numerous functionalized molecules. In both cases, the presence of NMP as cosolvent (THF/NMP) is determinant. For preparative organic chemistry, these two reactions compare favorably to the other related procedures since they are very easy to carry out and involve no toxic or expensive product. The Fe-catalyzed reaction is the first general Fe-catalyzed alkenylation procedure of preparative interest since no excess of alkenyl halides is required and even alkenyl chlorides can be used successfully.