The Heaviest Bottleable Metallylone: Synthesis of a Monatomic, Zero‐Valent Lead Complex (“Plumbylone”)

The elusive plumbylone {[Si(II)(Xant)Si(II)]Pb(0)} 3 stabilized by the bis(silylene)xanthene chelating ligand 1, [Si(II)(Xant)Si(II)=PhC(NtBu)(2)Si(Xant)Si(NtBu)(2)CPh], and its isolable carbonyl iron complex {[Si(II)(Xant)Si(II)]Pb(0)Fe(CO)(4)} 4 are reported. The compounds 3 and 4 were obtained stepwise via reduction of the lead(II) dibromide complex {[Si(II)(Xant)Si(II)]PbBr(2)} 2, prepared from the bis(silylene)xanthene 1 and PbBr(2), employing potassium naphthalenide and K(2)Fe(CO)(4), respectively. While the genuine plumbylone 3 is rather labile even at −60 °C, its Pb(0)→Fe(CO)(4) complex 4 turned out to be relatively stable and bottleable. However, solutions of 4 decompose readily to elemental Pb and {[Si(II)(Xant)Si(II)]Fe(CO)(3)} 5 at 80 °C. Reaction of 4 with [Rh(CO)(2)Cl](2) leads to the formation of the unusual dimeric [(OC)(2)RhPb(Cl)Fe(CO)(4)] complex 6 with trimetallic Rh−Pb−Fe bonds. The molecular and electronic structures of 3 and 4 were established by Density Functional Theory (DFT) calculations.