Phosphagermaallene Mes*PCGe(t-Bu)Tip 1 (Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl) has been obtained by an improved synthesis in relation to the previously reported preparation starting from t-BuGeCl3. Very short GeC (1.761(2) Å) and PC (1.625(2) Å) double bond lengths, trigonal planar geometry around the Ge atom, and GeCP bond angle of 166.57° are indicative of an heteroallenic structure for 1. Its reactions with crotonaldehyde and cinnamaldehyde lead to 1-oxa-2-germacyclobutanes by a [2 + 2] cycloaddition between the GeC and CO double bonds; with methyl vinyl ketone, both a [2 + 4] cycloaddition between the GeC and the OC−CC moieties and an ene-reaction are observed leading to a 1-oxa-2-germacyclohex-5-ene and a germyl(butadienyl)ether, respectively. With acetophenone, an ene-reaction occurs to afford exclusively a germyl(vinyl)ether. DFT calculations have been performed to explain the regiochemistry observed.
Chalcogenagermiranes that feature an exocyclic PdC double bond were obtained from the phosphagermaallene Mes*Pd CdGe(t-Bu)Tip (Mes* ) 2,4,6-tritert-butylphenyl, Tip ) 2,4,6triisopropylphenyl) and heaVier chalcogens. The structural data of selena-and telluragermiranes show they are intermediate between a normal three-membered ring and a π-complex.
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