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.