Synthesis and Reactivity of Ion‐Separated Salts [K(18‐Crown‐6)][(Me ₂ ‐cAAC)GeE(SiMe ₃ ) ₃ ] and [K(2.2.2‐Cryptand)][(Me ₂ ‐cAAC)GeE(SiMe ₃ ) ₃ ] (E = Si, Ge): Base‐Stabilised Germylidenides or Germenyl Anions?

The ion‐separated salts [K(18‐crown‐6)][(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] ( 1a,b ) and [K(2.2.2‐cryptand)][(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] ( 2a,b ) ( a , E = Si; b , E = Ge; Me 2 ‐cAAC = 1‐(2′,6′‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidine‐2‐ylidene) were synthetised via stoichiometric reaction of K[(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] and 18‐crown‐6 or [2.2.2]cryptand in THF at room temperature. Structural, spectroscopic, and computational characterisation of the ‘naked’ anions [(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] − showed that they can be described with a resonance between base‐stabilised germylidenide and germenyl anion formulations. The reaction of CO 2 with 1a gave a formal [2+2] cycloaddition product ( 3 ), whereas the contact ion pair salts K[(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] give μ‐CO 2 ‐ κC : κO complexes [(Me 2 ‐cAAC)Ge{C(O)OSiMe 3 }E(SiMe 3 ) 3 ] or radicals [(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] • . The mechanism for the formation of 3 was analysed computationally, and the differing reactivity of 1 and K[(Me 2 ‐cAAC)GeE(SiMe 3 ) 3 ] with CO 2 was rationalised in terms of the electronic structure of the anion that is modulated by the coordinating vs. noncoordinating nature of the counter ion.