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[B12Cl12]) 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. Journey through a maze: Only guided by 119Sn and 29Si NMR spectroscopy, the synthesis of cyclic bissilylstannylene 3 was accomplished. Finally, the key to success was the use of bulky tBuMe2Si groups and carefully designed cation exchange reactions applying salts of weakly coordinating anions (see figure).