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

The monoatomic zero-valent tin complex (stannylone) {[Si-II(Xant)Si-II]Sn-0} 5 stabilized by a bis(silylene)xanthene ligand, [Si-II(Xant)Si-II=PhC(NtBu)(2)Si(Xant)Si(NtBu)(2)CPh], and its bis-tetracarbonyliron complex {[Si-II(Xant)Si-II]Sn-0[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 Sn-II halide precursor {[Si-II(Xant)Si-II](SnCl)-Cl-II}Cl 2 or {[Si-II(Xant)Si-II]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 pi-type lone pair with delocalization into both adjacent vacant orbitals of the Si-II atoms and a sigma-type lone pair at the Sn-0 center, respectively, indicating genuine stannylone character.