Terphenyl Ligand Stabilized Lead(II) Derivatives of Simple Organic Groups: Characterization of Pb(R)C₆H₃-2,6-Trip₂(R = Me, t-Bu, or Ph; Trip = C₆H₂-2,4,6-i-Pr₃), {Pb(μ-Br)C₆H₃-2,6-Trip₂}₂, py·Pb(Br)C₆H₃-2,6-Trip₂(py = Pyridine), and the Bridged Plumbylyne Complex [{W(CO)₄}₂(μ-Br)(μ-PbC₆H₃-2,6-Trip₂)]

Abstract

The reaction between 1 equiv of the sterically encumbered lithium terphenyl Et2O·LiC6H3-2,6-Trip2 and PbBr2 in diethyl ether afforded the organolead(II) halide compound {Pb(μ-Br)C6H3-2,6-Trip2}2 (1) as orange crystals. Treatment of 1 with a stoichiometric amount of pyridine (py) gave the complex py·Pb(Br)C6H3-2,6-Trip2 (2) as yellow needles. The addition of 1 equiv of methylmagnesium bromide, tert-butyllithium, or phenyllithium to 1 resulted in the diorganolead(II) compounds Pb(R)C6H3-2,6-Trip2 (R = Me, 3; t-Bu, 4; or Ph, 5) in good yield. The compounds 3 and 5 are the first stable, monomeric lead(II) derivatives involving the simplest alkyl and aryl groups Me and Ph. Reaction of 1 with W(CO)5THF did not yield the expected plumbylene complex (CO)5W{Pb(Br)C6H3-2,6-Trip2}. Instead, the bridged plumbylyne species [{W(CO)4}2(μ-Br)(μ-Pb-C6H3-2,6-Trip2)] (6) was obtained in low yield. All compounds were characterized by X-ray crystallography, 1H and 13C NMR, IR, and UV−vis spectroscopy. 207Pb NMR spectra of 3−5 were also obtained. The results demonstrate the effectiveness of the terphenyl ligand in creating a protected cavity at a site in which normally unstable moieties are stabilized against decomposition reactions.