Reactivity of Divalent Germanium Alkoxide Complexes Is in Sharp Contrast to the Heavier Tin and Lead Analogues

The chemistry of β-diketiminate germanium alkoxide
complexes
has been examined and shown to be in sharp contrast to its heavier
congeners. For instance, (BDI)­GeOR (BDI = [{N­(2,6-iPr2C6H3)­C­(Me)}2CH], R = iPr, sBu, tBu) does not react with carbon
dioxide to form a metal carbonate complex. Addition of aliphatic electrophiles,
such as methyl iodide or methyl triflate, results in the net oxidative
addition to the germanium, giving cationic tetravalent germanium complexes,
[(BDI)­Ge­(Me)­OR]­[X] (X = I, OTf). An examination of the contrasting
reactivities of the alkoxide ligand and the germanium loan pair with
Lewis acids yielded the unusual germanium­(II)–copper­(I) adduct,
{μ2-Cu2I2}­[(BDI)­GeOtBu]2. This complex not only displays
a rare example of a divalent Ge–Cu bond, but is the first example
in which a planar Cu2I2 diamond core possesses
a three-coordinate copper bound to another metal center.