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

Abstract

Arylgermanes of the types ArGeH 3 , Ar 2 GeH 2 , and Ar 3 GeH 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 LiAlH 4 . This method is also applicable for aryl groups with sensitive substituents, as demonstrated for (4-methoxyphenyl)germane (p-anisylgermane, MeOC 6 H 4 GeH 3 ). With modified stoichiometry, bis(p-anisyl)germane is also available. The insertion of GeCl 2 into the C-Br bond of arylbromides using catalytic amounts of anhydrous AlCl 3 proved to be an efficient alternative if the reaction was carried out in the absence of a solvent. After LiAlH 4 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 73 Ge (s ) 9/2) NMR spectroscopy. Very surprisingly, sharp multiplet signals were observed with well-resolved 1 J(Ge,H) couplings. The molecular structure of p-MeOC 6 H 4 GeH 3 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.

Intermolecular interactions in group 14 hydrides: Beyond CH···HC contacts

“…A similar analysis of the GeH···HGe contacts discloses a group of structures (fibpub, kajzok, GeD 4 , pallev, larpid, qelyip, papzai) with Ge···Ge distances shorter than the van der Waals radii sum (4.58 Å) that may or may not show simultaneous short Ge···H (< 3.49 Å) contacts, but all of them have H···H contacts longer than 2.7 Å. In most cases the interaction topology is of type 2 involving GeH 3 or GeH 2 groups, while in one case (fibpub) a 3:3 staggered conformation 4 , in another case the 1 type interaction (qelyip), and in yet another case a colinear 3 interaction (papzai) is found.…”

“…For silicon, an angular dependence of the R 3 SiAHÁÁÁHASiR 3 contact distances is seen in the CSD (Figure 1), whereby the closer the two interacting silyl groups are to being colinear (measured by the average SiAHÁÁÁSi angle), the shorter the HÁÁÁH distance can be, with several nearly collinear contacts being at distances shorter than 2.8 Å. [41,[57][58][59][60][61] A similar analysis of the GeAHÁÁÁHAGe contacts discloses a group of structures (fibpub, [62] kajzok, [63] GeD 4 , [64] pallev, [65] larpid, [66] qelyip, [67] papzai [68] ) with GeÁÁÁGe distances shorter than the van der Waals radii sum (4.58 Å) that may or may not show simultaneous short GeÁÁÁH (< 3.49 Å) contacts, but all of them have HÁÁÁH contacts longer than 2.7 Å. In most cases the interaction topology is of type 2 involving GeH 3 or GeH 2 groups, while in one case (fibpub) [62] a 3:3 staggered conformation 4, in another case the 1 type interaction (qelyip), [67] and in yet another case a colinear 3 interaction (papzai) [68] is found.…”

Stable Monomeric Germanium(II) and Tin(II) Compounds with Terminal Hydrides

“…[3a, [14][15][16] The SnÀH stretching mode of 4 (1849 cm À1 ) is comparable to those in the hydrogen-bridged tin compound [{2,6-Trip 2 C 6 H 3 SnA C H T U N G T R E N N U N G (m-H)} 2 ] (1828, 1771 cm À1 ). [4] In the 1 H NMR spectrum of 3, the GeÀH hydrogen atom resonates at lower field (d = 8.08 ppm) than those in Ar'(H)GeGe(H)Ar' (d = 3.48 ppm) and Ar'(H) 2 GeGeAr'·PMe 3 (d = 3.81 ppm).…”

Synthetic, Structural, and Physical Aspects of Organo-Oligogermanes

“…This coupling constant is large compared to other 1 J Ge -H coupling constants, which typically range from 90-95 Hz. [96] For example, the 73 Ge NMR spectrum of GeH 4 exhibits a 1 J Ge -H coupling constant of 97.6 Hz, [97] while a coupling constant of 95.5 Hz was reported for the digermane Ge 2 H 6 and coupling constants of 94 and 90 Hz were reported for the peripheral and central germanium atoms, respectively, of Ge 3 H 8 . [92] …”