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

Here, we report the use of an alkyne‐functionalized amidine, PhC{N(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 = PhC{N(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)Ge}EPh] 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)Ge{TEMPO}] 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.