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

The monoatomic zero-valent tin complex (stannylone) {[SiII (Xant)SiII ]Sn0 } 5 stabilized by a bis(silylene)xanthene ligand, [SiII (Xant)SiII =PhC(NtBu)2 Si(Xant)Si(NtBu)2 CPh], 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 ]SnII Cl}Cl 2 or {[SiII (Xant)SiII ]SnBr2 } 3 through reductive salt-metathesis reaction with K2 Fe(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.