Abstract1‐Alkenes are converted in high yields to the corresponding primary diorganomagnesium compounds by transition metalcatalyzed hydromagnesation reaction using catalytically prepared suspended (MgH2*) or dissolved magnesium hydride (MgH2*). The most active hydromagnesation catalysts have been found to be combinations of zirconium tetrahalides with MgH2* or MgH2*. The reaction is highly regio‐and chemoselective. The diorganomagnesium compounds prepared in situ from magnesium, hydrogen, and 1‐alkenes can be applied to the synthesis of organic and organometallic compounds just as Grignard compounds (Scheme 3, reaction 3–11). Dioctylmagnesium undergoes the growth reaction with ethene in the presence of quinuclidine and is oxidized by molecular oxygen in high yield to 1