The Heaviest Bottleable Metallylone: Synthesis of a Monatomic, Zero-Valent Lead Complex ("Plumbylone").

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