Cation-Triggered Stannate(II)/Stannylenoid/Stannylene Conversion

The reaction of dipotassio-tetrasilan-1,4-diide (4) with anhydrous SnCl₂ at low temperature results in the formation of a five-membered cyclic potassio chlorostannate(II) ([(18-C-6)K](1)). By careful cation exchange reactions, it was transformed into the sodium chlorostannylenoid 2 (by using Na₂ [B₁₂ Cl₁₂ ]) or into the non-stabilized cyclic bissilylstannylene 3 (through applying Li[Al(OC(CF₃ )₃ )₄ ]). The increasing Lewis basicity of the bissilylstannylene 3 was analyzed by combined methods of DFT calculations and NMR spectroscopy and substantiated by the synthesis of the corresponding iron carbonyl complexes 7 and 8 from the chlorostannate 1 and the stannylene 3, respectively.