Synthesis and Tunable Reactivity of N-Heterocyclic Germylene

Modifying the beta-diketimine ligand LH 1 (LH=[ArN?C(Me)?CH?C(Me)?NHAr], Ar=2,6-iPr2C6H3) through replacement of the proton in 3-position by a benzyl group (Bz) leads to the new BzLH ligand 2, which could be isolated in 77?% yield. According to 1H NMR spectroscopy, 2 is a mixture of the bis(imino) form [(ArN?C(Me)]2CH(Bz) 2a and its tautomer [ArN?C(Me)?C(Bz)?C(Me)NHAr] 2b. Nevertheless, lithiation of the mixture of 2a and 2b affords solely the N-lithiated beta-diketiminate [ArN?C(Me)?C(Bz)?C(Me)?NLiAr], BzLLi 3. The latter reacts readily with GeCl2 center dot dioxane to form the chlorogermylene BzLGeCl 4, which serves as a precursor for a new zwitterionic germylene by dehydrochlorination with LiN(SiMe3)2. This reaction leads to the zwitterionic germylene BzL'Ge: 5 (BzL'=ArNC(?CH2)C(Bz)?C(Me)NAr) which could be isolated in 83?% yield. The benzyl group has a distinct influence on the reactivity of zwitterionic 5 in comparison to its benzyl-free analogue, as shown by the reaction of 5 with phenylacetylene, which yields solely the 1,4-addition product 6, that is, the alkynyl germylene BzLGeCCPh. Compounds 26 have been fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.