- Reactivity studies of N-heterocyclic carbene complexes of germanium(II)
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The chemistry of three N-heterocyclic carbene (NHC) complexes of GeR 2, where R = Cl (1), OtBu (2), Mes (3) (Mes = 2,4,6-trimethylphenyl), toward 2,3-dimethylbutadiene (DMB), 3,5-di-tert- butylorthoquinone, methyl iodide, pivalic acid, and benzophenone is reported. Upon heating, 2 and 3 cyclize with DMB to yield a germacyclopentene and free NHC. In contrast, 1 does not react with DMB. PB1PBE/6-311+G(d,p) model chemistry shows that the cycloaddition reactions of NHC-GeX2 (X = F, Cl) with butadiene are not thermodynamically favorable. 3,5-Di-tert-butylorthoquinone reacts rapidly with 1-3 to form cyclic products; in the case of 1 and 2, the NHC remains coordinated to the germanium, resulting in a hypervalent species. Compounds 1-3 react with methyl iodide by displacement of I-; in each case [NHC-GeR2Me]+ is produced. Only compound 3 reacts in a controlled fashion with pivalic acid; both 1:1 and 1:2 adducts were characterized. Benzophenone failed to react with 1 or 2 but did undergo cycloaddition with 3. In comparison with uncomplexed GeR2 species, the NHC-GeR2 complexes are less reactive. The prospect of using NHC-GeR2 as a synthon for GeR2 appears to be reaction specific.
- Rupar, Paul A.,Staroverov, Viktor N.,Baines, Kim M.
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p. 4871 - 4881
(2011/02/22)
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- On the synthesis, structure, and reactivity of tetramesityldigermene
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Tetramesityldigermene (1) can be synthesized cleanly and quantitatively by photolysis of hexamesitylcyclotrigermane (2) in THF at low temperature. A solution of tetramesityldigermene (1) in THF is stable for several weeks at room temperature; the digermene does not dissociate or rearrange. The molecular structure of tetramesityldigermene (1) has been determined using X-ray crystallography. The effectiveness of the new protocol for the synthesis of tetramesityldigermene (1) and its derivatives has been demonstrated in the study of the addition of carboxylic acids to tetramesityldigermene (1).
- Hurni, Krysten L.,Rupar, Paul A.,Payne, Nicholas C.,Baines, Kim M.
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p. 5569 - 5575
(2008/10/09)
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