The above mentioned Co(0) complexes have been already successfully used to promote Reformatsky-type [18] and aldol-type [19] reactions and are easily prepared from Co(II) salts by reduction with magnesium metal in the presence of a selected phosphine. [20] They can be used either in stoichiometric or in substoichiometric (catalytic) amounts, provided, in the latter case, magnesium metal is present, to carry out the reduction from Co(II) to Co(0).
