A Genuine Stannylone with a Monoatomic Two-Coordinate Tin(0) Atom Supported by a Bis(silylene) Ligand

Abstract

The monoatomic zero-valent tin complex (stannylone) {[SiII(Xant)SiII]Sn0} 5 stabilized by a bis(silylene)xanthene ligand, [SiII(Xant)SiII=PhC(NtBu)2Si(Xant)Si(NtBu)2CPh], and its bis-tetracarbonyliron complex {[SiII(Xant)SiII]Sn0[Fe(CO)4]2} 4 are reported. The stannylone 5 bearing a two-coordinate zero-valent tin atom is synthesized by reduction of the precursor 4 with potassium graphite. Compound 4 results from the SnII halide precursor {[SiII(Xant)SiII]SnIICl}Cl 2 or {[SiII(Xant)SiII]SnBr2} 3 through reductive salt-metathesis reaction with K2Fe(CO)4. According to density functional theory (DFT) calculations, the highest occupied molecular orbital (HOMO) and HOMO-1 of 5 correspond to a π-type lone pair with delocalization into both adjacent vacant orbitals of the SiII atoms and a σ-type lone pair at the Sn0 center, respectively, indicating genuine stannylone character.