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 Et 2 O‚LiC 6 H 3 -2,6-Trip 2 and PbBr 2 in diethyl ether afforded the organolead(II) halide compound {Pb(µ-Br)C 6 H 3 -2,6-Trip 2 } 2 (1) as orange crystals. Treatment of 1 with a stoichiometric amount of pyridine (py) gave the complex py‚Pb(Br)C 6 H 3 -2,6-Trip 2 (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)C 6 H 3 -2,6-Trip 2 (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) 5 THF did not yield the expected plumbylene complex (CO) 5 W{Pb(Br)C 6 H 3 -2,6-Trip 2 }. Instead, the bridged plumbylyne species [{W(CO) 4 } 2 (µ-Br)(µ-Pb-C 6 H 3 -2,6-Trip 2 )] ( 6) was obtained in low yield. All compounds were characterized by X-ray crystallography, 1 H and 13 C NMR, IR, and UV-vis spectroscopy. 207 Pb 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.

Tungsten–Lead Triple Bonds: Syntheses, Structures, and Coordination Chemistry of the Plumbylidyne Complexes trans‐[X(PMe3)4WPb(2,6‐Trip2C6H3)]

“…It crystallizes as a centrosymmetric iodide‐bridged dimer, which features a Pb 2 I 2 parallelogram with a Pb⋅⋅⋅Pb separation of 4.603(1) Å17 and two quite different PbI bond lengths (2.9499(7) and 3.2764(8) Å) and internal bond angles (84.81(2) and 95.19(2)°; Figure 1). The PbC aryl bond length of 1 ‐I at 2.326(6) Å compares well with those of 1 ‐Br (2.306(13) and 2.329(11) Å) 14. Heating a solution of cis ‐[W(N 2 ) 2 (PMe 3 ) 4 ] with a stoichiometric amount of 1 ‐Br or 1 ‐I in toluene at 100 °C was accompanied by a rapid color change from orange to red‐brown to afford the plumbylidyne complex 2 ‐Br and 2 ‐I, respectively (Scheme ) 15.…”

“…15 The isostructural, trans ‐configured octahedral complexes have approximate C 2 point group symmetry,20 and display almost linear W‐Pb‐C aryl linkages ( 2 ‐Br, 177.5(2)°; 2 ‐I, 175.79(8)°) and the shortest WPb bonds ( 2 ‐Br, 2.5464(5) Å; 2 ‐I, 2.5477(3) Å) reported to date 21. In fact, the WPb bond lengths of 2 ‐Br and 2 ‐I are 0.20 Å shorter than those of the bridged plumbylidyne complex [{W(CO) 4 } 2 (μ‐Br){μ‐Pb(2,6‐Trip 2 C 6 H 3 )}] (2.7423(3) and 2.7517(3) Å), which contains a three‐coordinate lead center with trigonal‐planar geometry,14 and approximately 0.45 Å shorter than the WPb single bonds of the V‐shaped tungstenoplumbylene [Pb(2,6‐Trip 2 C 6 H 3 ){W(η 5 ‐C 5 H 5 )(CO) 3 }] (2.9809(10) and 3.0055(6) Å) 21d. The PbC aryl bonds of 2 ‐Br (2.254(6) Å) and 2 ‐I (2.258(3) Å) are shorter than those of 1 ‐Br and 1 ‐I (Figure 1), or those reported for the plumbylenes [Pb(2,6‐Trip 2 C 6 H 3 )R] (R=Me, t Bu, Ph: PbC aryl 2.272(9)–2.321(3) Å)14 and metalloplumbylenes [Pb(2,6‐Trip 2 C 6 H 3 ){M(η 5 ‐C 5 H 5 )(CO) 3 }] (M=Cr, Mo, W: PbC aryl 2.278(9)–2.294(4) Å),21d and indicate that the triply bonded lead atom uses sp‐hybrid orbitals for σ bonding.…”

“…Starting materials were the dinitrogen complexes cis ‐[W(N 2 ) 2 (PMe 3 ) 4 ] and [W(N 2 )(PMe 3 ) 5 ]13 and the aryllead( II ) halides [{Pb(2,6‐Trip 2 C 6 H 3 )X} 2 ] (X=Br ( 1 ‐Br), I ( 1 ‐I)). Compound 1 ‐I was prepared by metathetical exchange of 1 ‐Br14 with NaI in diethyl ether. It was isolated in 82 % yield as an air‐sensitive, bright orange solid, which melts at 222 °C and decomposes at 235 °C to give an oily, red mass 15.…”

Fundamental Coordination Chemistry, Environmental Chemistry, and Biochemistry of Lead(II)

“…This molecule exhibits a bent geometry with a PbÀ ÀPbÀ ÀC angle of 94.3 and exhibits a stereochemically active lone pair on each metal. The Pb À À À À À À Pb triply bonded compound is particularly interesting because it constitutes the first example of a heavier group 14 (VIA) analogue of acetylene (192).…”

Synthesis and some reactivity studies of germanium, tin and lead analogues of alkynes

“…6,7 The iodides can be converted quantitatively to their lithium salts by treatment with n BuLi. 8 The lithium salts can then be used as transfer agents to synthesize the divalent arylelement(II) halide derivatives as shown in Eqn (1): 9,10 ArLi + EX 2 −−−→ ArEX + LiX…”