In the presence of a second equivalent of the main group hydride, the products of -alkyl migration are not stable. Addition of 1 to the ring-opened pent-5-en-1-ylmagnesium complex 6b resulted in a second anti-Markovnikov hydromagnesiation reaction, yielding the 1,5dimagnesio pentane 8b. Similarly a second hydrozincation of 7a yields the 1,4-dizincio butane complex 9a (Figure ).