148731-81-1Relevant articles and documents
On mixed group 14-group 14 bonds. 8. Asymmetrically substituted compounds Ar3Pb-GeAr′3 and Ar3Pb-PbAr′3: Comparison of structure and physical behavior in the series of bonds Sn-Sn, Pb-Ge, Pb-Sn, and Pb-Pb
Koglin, Hans-Jürgen,Behrends, Kerstin,Dr?ger, Martin
, p. 2733 - 2742 (2008/10/08)
A general procedure for the synthesis of hezaarylated compounds of the type Ar3PbGeAr′3 from Ar3PbLi and Ar′3GeX in THF/ether at -60°C is given. Likewise, from Ar3PbLi and Ar′PbI the asymmetrical diplumbanes Ar3PbPbAr′3 could be prepared. By the use of the bulky groups Ar and Ar′, the migration of aryl groups could be suppressed, avoiding the appearance of the mixtures Pb2Ar6-nAr′n (n = 0-6). Nonetheless, the resulting diplumbanes Ar3Pb-PbAr′3 were always partially contaminated with some symmetric Pb2Ar6 and Pb2Ar′6. The structures of (p-Tol)3PbGePh8 (triclinic, space group P1; a = 9.983(1) b = 12.201(1) c = 15.728(2) A?; α = 95.73(1), β = 103.56(1), γ = 113.06(1)°; V = 1674(1) A?3; Z = 2; R = 0.0434) and (p-Tol)3PbGe-(p-Tol)3 (trigonal, space group R3; a - 13.338(1), c = 36.55(1) A?; V = 5631(2) A?3; Z = 6; R = 0.0522) have been determined. NMR chemical shifts δ(119Sn) and δ(207Pb) (40 compounds) and one-bond couplings 1J(M-M′) (16 compounds), stretching vibrations ν(M-M′) and force constants f(M-M′) for a diatomic oscillator (38 compounds), and bond distances d(M-M′) (18 compounds) are compared for all six combinations M/M′ = Ge/Sn/Pb of Ar3M-M′Ar′3. Concerning the asymmetric diplumbanes Ar3Pb-PbAr′3, assignments of δ(207Pb) resulted from a consideration of inductivity (comparison to PbAr4/Ar′4) and an assumed order of charge flow Δ(Ar ? Ar′) (13 compounds). Sequences exist for δ(119Sn) (Pb-Sn > Sn-Sn ≥ Sn-Ge), δ(207Pb) (Pb-Pb > Pb-Sn ≈ Pb-Ge), f (Sn-Ge > Sn-Sn ≥ Pb-Sn, and Pb-Ge > Pb-Sn ≥ Pb-Pb), d (Sn-Ge ≤ Pb-Ge 1K (Pb-Sn > Sn-Sn > Pb-Pb scatter ). The polarities Pbδ--Geδ+and Pbδ- - Snδ+ are obvious. The enhanced electronegativity of lead demonstrates the influence of its relativistically contracted 6s and 6p orbitals. With regard to Ar3Pb-PbAr′3, a relation between 1K(Pb-Pb) and the charge flow Δ(Ar ? Ar′) is indicated.
