Dehydrogenative Double C-H Bond Activation in a Germylene-Rhodium Complex**

Transition metal tetrylene complexes offer great opportunities for molecular cooperation due to the ambiphilic character of the group 14 element. Here we focus on the coordination of germylene [(Ar-Mes2)(2)Ge :] (Ar-Mes=C6H3-2,6-(C6H2-2,4,6-Me-3)(2)) to [RhCl(COD)](2) (COD=1,5-cyclooctadiene), which yields a neutral germyl complex in which the rhodium center exhibits both eta(6)- and eta(2)-coordination to two mesityl rings in an unusual pincer-type structure. Chloride abstraction from this species triggers a singular dehydrogenative double C-H bond activation across the Ge/Rh motif. We have isolated and fully characterized three rhodium-germyl species associated to three C-H cleavage events along this process. The reaction mechanism has been further investigated by computational means, supporting the key cooperative action of rhodium and germanium centers.