Reversible Dihydrogen Splitting and Diradical Reactivity of 1,4‐Digermabenzene‐1,4‐diide

Here, we report the use of an alkyne‐functionalized amidine, PhCN (Dipp) N (Dipp) C≡CSiMe 3 (1) (Dipp = 2, 6‐ i Pr 2 C 6 H 3), to access a range of Ge (IV), Ge (II/IV), Ge (II), and Ge (I) compounds based on an anionic dicarbene (ADC) framework (ADC = PhCN (Dipp) C 2). The mixed‐valent Ge (II/IV) complex (ADC) GeCl 3 GeCl 2 (4) is obtained by partial reduction of (ADC) GeCl 3 GeCl 4 (3). Treatment of 1 with 3 affords the Ge (IV) chloride (ADC) GeCl 3 2 (5), which can be sequentially reduced with KC 8 to give the known Ge (II) and Ge (I) species (ADC) GeCl 2 (7) and (ADC) Ge 2 (8), respectively. The 1, 4‐digermabenzene‐1, 4‐diide (8) is a singlet diradical that cleaves dihydrogen at room temperature to form the Ge (II) hydride (ADC) GeH 2 (9) ; under vacuum, 9 regenerates 8. Compound 8 reacts with azobenzene and diphenylacetylene to yield the corresponding 4+2‐cycloaddition products, (ADC) GeEPh 2 10 (E = N) and 11 (E = C), respectively. Treatment of 8 with TEMPO (2, 2, 6, 6‐tetramethylpiperidinyloxyl) produces the radical coupling product, the bis (TEMPO‐germylene) (ADC) GeTEMPO 2 (13). All compounds were characterized by spectroscopic methods, and their molecular structures, including that of 9, unknown previously, were confirmed by single‐crystal X‐ray diffraction.