Oligogermanes Containing Only Electron-Withdrawing Substituents: Synthesis and Properties

Abstract

A series of germanes Ar 3 GeX, containing electron-withdrawing substituents [Ar = p-FC 6 H 4 , 1a−d, 1a (X = Cl), 1b (X = Br), 1c (X = H), 1d (X = NMe 2 ); p-F 3 CC 6 H 4 , 2a−d, 2a (X = Cl), 2b (X = Br), 2c (X = H), 2d (X = NMe 2 )], was synthesized and used to prepare symmetrical digermanes Ar 3 Ge−GeAr 3 , (p-FC 6 H 4 ) 3 GeGe(C 6 H 4 F-p) 3 (3), and (p-F 3 CC 6 H 4 ) 3 GeGe(C 6 H 4 CF 3 -p) 3 (4) and trigermane [(p-F 3 CC 6 H 4 ) 3 Ge] 2 Ge(C 6 F 5 ) 2 ( 5) by hydrogermolysis reaction. The properties of all compounds were investigated by multinuclear NMR and for oligogermanes by UV/vis and fluorescence spectroscopy, as well as by electrochemical methods. In addition, the molecular structures of 1a, 1b, 2b, 2c, and 3−5 were studied by X-ray diffraction analysis. Compound 5 showed a significantly shifted UV/visible absorption to the red field in comparison with previously described derivatives.

Aryl Oligogermanes as Ligands for Transition Metal Complexes

“…Ge–Ge bond length [2.4266(9) vs. 2.4284(6) vs. 2.4316(13) Å in 3c , 4a , 5a , respectively] and Ge–C bond length [for example, Ge–C ArM 1.972(6) vs. 1.970(6) vs. 1.974(9) Å]. Furthermore, the d (Ge–C ArM ) is longer than the other Ge–C bonds; this may be explained as by steric reasons [introduction of a more voluminous M(CO) 3 substituent] and by electronic effects (similar to ones, which have been earlier observed for donor‐acceptor oligogermanes) , . In general, the geometry at each of Ge atom may be described as a slightly distorted tetrahedral.…”

Donor-acceptor molecular oligogermanes: Novel properties and structural aspects

“…Furthermore, this method has been limited by the compatibility of some of the initial reagents. For instance, it is impossible to use geminal polyamides, R2Ge[NMe2]2, to construct the Ge-Ge bond [13] . Although the corresponding vicinal diamides, Me2NGePh2GePh2NMe2 [14] , and branched monoamides, [Ph3Ge]3GeNMe2 [15] , are known and are sufficiently stable to be used under hydrogermolysis conditions, there is no data in the literature on using linear catenated germylmonoamide and their application in Ge-Ge bond formation.…”

“…It was previously established that the physical properties of the oligogermanes highly depend on the nature of the substituent, on their geometrical volume, on the number of Ge atoms in the chain and on the overall conformation of the molecule. Thus, the introduction of donating groups destabilize the HOMO [16] level, whereas the presence of withdrawing groups resulted in a stabilization of the LUMO [10,13] , by improving the σ-conjugation. The same effect is observed when the Ge chain is elongated.…”

“…Compounds 3 and 4 were isolated as white air-and moisture stable powders in high yields (78 and 84 %, respectively). The structure of these compounds in solution was confirmed by multinuclear NMR spectroscopy ( 1 H, 13 C, 19 F) and their composition was established on the basis of elemental analysis. In general, 1 H and 13 C NMR spectra for both compounds are very similar.…”

“…1, 3; Supporting Information, Table S1). Up todayonly 12 linear molecular trigermanes have been studied by XRD (for details see [13] ), where Ge-Ge bond length and Ge-Ge-Ge angle vary between 2.413-2.6223 Å and 110.4-125.00 o , respectively, depending on the steric size and on the electronic nature of the substituents located at Ge atoms. Compound 3 crystallizes in the P-1 space group (Z = 2).…”