A reversible two-electron redox system involving a divalent lead species

Abstract

Reduction of THF-stabilized plumbacyclopentadienylidene with lithium afforded dilithioplumbole. On the other hand, oxidation of the dilithioplumbole provided the starting plumbacyclopentadienylidene. This is the unprecedented example of a reversible interconversion between group 14 M(II) and its dianionic species bearing organic substituents.

Synthesis and reactivity of a ruthenocene-type complex bearing an aromatic π-ligand with the heaviest group 14 element

“…In the 13 C NMR spectra, the signals of C α of 5 (151.94 ppm) and 6 (149.76 ppm) were found in a field higher than those of 7 (176.20 ppm) and 8 (170.70 ppm). In the 13 C NMR spectra of the stannole and plumbole derivatives, 12 , 16 , 26 the chemical shifts for the C α nuclei are highly dependent on the electronic states of the tin and lead atoms: the C α nuclei of dilithiometalloles, which have dianionic character, resonate in a field lower (approximately 225 ppm for dilithioplumboles) than those for lithiometalloles (approximately 205 ppm for a lithioplumbole), bearing monoanionic character. The NMR signals for the C α nuclei of 1,1-diphenylmetalloles are observed in a much higher field (for example, 150 ppm for hexaphenylplumbole).…”

“… 15 The coordination mode of the resulting ruthenocene derivatives ( 2 ) is highly dependent on the substituent on the tin atom, and the complexes composed of η 5 -coordinating stannole ligands are oxidized more easily than the germole complex. 10 a These findings prompted us to apply plumbole anions and dianions 16 as ligands, which would be envisaged to be more electron-donating than the tin analogs because a lead atom is the heaviest among the group 14 atoms. In terms of sandwich complexes bearing ligands containing the 6th row elements, a bismaferrocene and a dibismaferrocene have been reported.…”

The aromatic dianion metalloles

“…In 2010, Saito and co-workers reported the heaviest group 14 congener of the cyclopentadienyl (Cp) analog, dilithioplumbole 9 (dilithio-Pb) ( Scheme 6 ). 19 a The dilithio-Pb 9 was synthesized by the reduction of hexaphenylplumbole with lithium, a similar synthetic method to that used for dilithio-Sn. Based on the single crystal X-ray structure, only one Li atom is coordinated with the plumbole ring in an η 5 fashion, while the other Li atom is solvated and far away from the Pb center (more than 10 Å).…”

Triple-decker complexes incorporating three distinct deck architectures

“…1B and C). 17 For the heaviest dianionic metallole, the plumbole, 18 only anionic sandwich-type Ru and = 1,4-bis-tert-butyldimethylsilyl-2,3-bis-phenyl-plumbolyl) and [Li(thf) 4 20 and another inverted sandwich Rh complex [{(cod)Rh} 2 (m,Z 5 -L Pb )] 20 were reported. Related trimetallic triple-decker species with three distinct deck motifs have remained elusive.…”

“…In our first attempt to synthesize a lead-containing polyphosphide, the dilithioplumbole [Li 2 (thf) 2 (m,Z 5 -L Pb )] 18 was reacted with white phosphorus (P 4 ) in toluene at room temperature for 16 h (Scheme 1). The colour of the solution turned from green to colourless concomitant with the precipitation of grey metallic powder.…”