Synthesis and One‐Electron Reduction of Donor‐Acceptor‐Stabilized Si ^II –E ^II –Si ^II Trimetallylenes (E = Ge, Sn, Pb)

Abstract

ABSTRACT Herein, we report isolable donor–acceptor‐stabilized Si II –E II –Si II trimetallylenes (E = Ge ( 2 ), Sn ( 3 ), Pb ( 4 ); Si II = Mes(cAAC)Si; Mes = 2,4,6‐Me 3 C 6 H 2 ; cAAC = C(CH 2 )(CMe 2 ) 2 N‐2,6‐ i Pr 2 C 6 H 3 ), stabilized by a cyclic alkylaminocarbene attached to the divalent Si atoms. They were synthesized through salt‐metathesis reactions of the dimeric silanylidene anion (Si II K) 2 1a and EX 2 precursors (X = Cl, N(SiMe 3 ) 2 ). Computational analyses reveal that 2–4 adopt bent donor–acceptor‐stabilized Si II –E II –Si II frameworks featuring polarized Si–C(cAAC) π interactions together with delocalized Si–E π interactions involving the Lewis‐acidic E II center. This donor–acceptor electronic structure results in small HOMO–LUMO gaps, giving rise to pronounced near‐infrared (NIR) absorption. Remarkably, the one‐electron reduction of 2 and 3 leads to the Ge I ‐ and Sn I ‐ radical anions 2 •− and 3 •− , respectively, thereby highlighting that this donor–acceptor motif can even stabilize heavy Group 14 elements in lower oxidation states.