Preparation, Structure, and ⁷³Ge NMR Spectroscopy of Arylgermanes ArGeH₃, Ar₂GeH₂, and Ar₃GeH

Arylgermanes of the types ArGeH₃, At₂GeH₂, and Ar₃GeH are important precursors for the preparation of oligo- and polygermanes. These precursors are readily prepared in good yields via an in situ Grignard reaction employing tetra(ethoxy)germane, an aryl halide, and magnesium metal in tetrahydrofuran as the reaction medium. The aryl-tri(ethoxy)germanes obtained were reduced to the germane hydrides with LiAIH₄. This method is also applicable for aryl groups with sensitive substituents, as demonstrated for (4-methoxyphenyl)germane (p-anisylgermane, MeOC₆H₄GeHa). With modified stoichiometry, bis(p-anisyl)gennane is also available. The insertion of GeCI₂ into the C-Br bond of arylbromides using catalytic amounts of anhydrous Aids proved to be an efficient alternative if the reaction was carried out in the absence of a solvent. After LiAlH₄ reduction of the aryltrihalogermanes, phenyl-,p-tolyl-, and mesitylgermane were obtained in good yields. The arylgermanes have been identified by their analytical and spectroscopic data, including ⁷³Ge (s = 9/2) NMR spectroscopy. Very surprisingly, sharp multiplet signals were observed with well-resolved ¹J(Ge,H) couplings. The molecular structure of p-MeOC₆H₄GeH₃ was determined from low-temperature X-ray diffraction data collected from a single-crystal grown "in situ" from the melt (mp: 15 °C). The significant distortions observed in the anisyl part of the structure and the conformation of the molecule are in excellent agreement with results of ab initio quantum chemical calculations (MP2/6-31G) of this compound.