Dehydrogenation of LGeH by a Lewis N-Heterocyclic Carbene Borane Pair under the Formation of L ' Ge and its Reactions with B(C6F5)(3) and Trimethylsilyl Diazomethane: An Unprecedented Rearrangement of a Diazocompound to an Isonitrile

Abstract

Herein we report the dehydrogenation of LGeH (1) [L = CH{(CMe)(2,6-IPr2C6H3N)}(2)] by a frustrated Lewis NHC borane pair under the formation of an imidazolium borate salt (2) and the heterocyclic germylene L'Ge (3) [L' = CH{(C=CH2)(CMe)(2,6-IPr2C6H3N)(2)}]. The reaction of 3 with B(C6F5)(3) in toluene results in the formation of a zwitterion containing a germylene moiety, [B(C6F5)(3)L '' Ge] (4) [L '' = CH{(CCH2)(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}], Subsequent treatment of 4 with 1 equiv of 1,3-di-tert-butylimidazol-2-ylidene (NHC) gives B(C6F5)(3)L"'Ge (5) [L"' = CH{(C=CH2)(CCH2B(C6F5)(3))(2,6-IPr2C6H3N)(2)}] under formation of the imidazolium cation, Moreover compound 3 reacts with trimethylsilyl diazomethane (N2CHSiMe3) to form the diazogermylene LGeC(N-2)SiMe3 (6) under C-H bond cleavage. Compound 6 slowly rearranges to the isonitriletrimethylsilyl germanium(II) amide LGeN(SiMe3)NC (6a). All compounds were characterized by microanalysis and multinuclear NMR spectroscopy. Compounds 4, 6, and 6a were unequivocally identified by single crystal X-ray structure analysis.