Persistent radicals of trivalent tin and lead

Marco Becker, Christoph Förster, Christian Franzen, Johannes Hartrath, Enzio Kirsten, Jörn Knuth, Karl W. Klinkhammer, Ajay Sharma, Dariush Hinderberger

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

In this report we present synthetic, crystallographic, and new electron paramagnetic resonance (EPR) spectroscopic work that shows that the synthetic route leading to the recently reported, first persistent plumbyl radical •PbEbt3 (Ebt = ethylbis(trimethylsilyl)silyl), that is, the oxidation of the related PbEbt3-anion, was easily extended to the synthesis of other persistent molecular mononuclear radicals of lead and tin. At first, various novel solvates of homoleptic potassium metallates KSnHyp 3 (4a), KPbHyp3 (3a), KSnEbt3 (4b), KPblDt 3 (3c), and KSnlbt3 (4c) (Hyp = tris(trimethylsilyl)silyl, lbt = isopropylbis(trimethylsilyl)silyl), as well as some heteroleptic metallates, such as [Li(OEt2)2][SnnBuHyp 2] (3d), [Li(OEt2)2][PbnBuHyp 2] (4d), [Li(thf)4][PbPhHyp2] (3e), and [K(thf)7][PbHyp2{N(SiMe3)2}] (3f), were synthesized and crystallographically characterized. Through oxidation by tin(II) and lead(II) bis(trimethylsilyl)amides or the related 2,6-di-tert-butylphenoxides, they had been oxidized to yield in most cases the corresponding radicals. Five novel persistent homoleptically substituted radicals, that is, •SnHyp3 (2a), •PbHyp3 (1a), •SnEbt3 (2b), •Snlbt3 (2c), and •Pblbt 3 (1c), had been characterized by EPR spectroscopy. The stannyl radicals 2a and 2c as well as the plumbyl radical 1c were isolated as intensely colored crystalline compounds and had been characterized by X-ray diffraction. Persistent heteroleptically substituted radicals such as •PbHyp 2Ph (1e) or •PbHyp2Et (1g) had also been generated, and some selected EPR data are given for comparison. The plumbyl radicals •PbR3 exhibit a clean monomolecular decay leading to the release of a temperature-dependent stationary concentration of branched silyl radicals. They may thus serve as tunable sources of these reactive species that may be utilized as reagents for mild radical silylations and/or as initiators for radical polymerizations. We present EPR-spectroscopic investigations for the new tin- and lead-containing compounds giving detailed insights into their electronic and geometric structure in solution, as well as structural studies on the crystalline state of the radicals, some of their anionic precursors, and some side-products.

Original languageEnglish (US)
Pages (from-to)9965-9978
Number of pages14
JournalInorganic chemistry
Volume47
Issue number21
DOIs
StatePublished - Nov 3 2008

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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