A T-shaped, Open-Shell Cobalto-Germylene Demonstrating Dynamic Covalent Bond Activation

Reaction of chelating cationic germylene ligand [PhiPDippGe]+ (1; PhiPDipp = {[Ph2PCH2Si(iPr)2](Dipp)N}; Dipp = 2,6-iPr2C6H3) with the NHC-stabilised Co0 system [IPr·Co(η2-vtms)2] gives ready access to the first example of an open-shell metallo-germylene in T-shaped Co complex 2, in high yields. Complex 2 is formed through the formal oxidative addition of the germylene to Co, giving a unique route to this compound class. The Co centre in 2 bears a high-spin density of its single unpaired electron, corroborated by SQUID magnetometry, EPR spectroscopy, and quantum-chemical calcula-tions. Detailed analysis of the electronic structure of 2 establish the distinct nature of the germanium cobalt interaction as an electron-sharing covalent bond. Still, the formation of 2 is not trivial: shortening reaction times leads to the formation of three different fragments of this species (viz. 3, 4, and 5), which can be isolated and fully characterised; further, these quantitatively recombine over extended reaction times in forming 2. This is borne out by trapping of one additional species, namely cobalto-germylene complex 7, through the addition of a Lewis base to dissolved 2, highlighting the highly dynamic collection of species formed in solution from dissolved 2.