Trihydrogermyl-substituted thiophenes

Treatment of 2-bromo- or 2,5-dibromo-thiophene with equivalent quantities o f n-butyllithium at low temperature, followed by bromogermane, afforded 2-g ermyl- 2 and 2,5-di(germyl)-thiophene 3 in 44 and 82% yields, respectively. The in situ Grignard reaction of 2-bromothiophene with tetra(ethoxy)german e and magnesium gave low yields of 2-[tri(ethoxy)germyl]thiophene 1. Attemp ts to convert this product into the trihydride using LiAlH4 yielded only tr aces of 2. Bis(2-thienyl)germane 4 is available from 2-lithiothiophene and dibromogermane (molar ratio 2:1, 64% yield). The products have been charact erized by analytical and spectroscopic methods. The Ge-73 NMR spectra show only broad resonances without discernible Ge-73-H-1 coupling owing to the l ow symmetry of the substituents. The molecular geometries of 2 and 3 have b een calculated using standard ab initio quantum chemical methods. The resul ts are similar to those for analogous silylthiophenes reported recently. Th ere is no evidence for significant intramolecular Ge . . .S interactions.