Liquid- and solid-state (CP-MAS) 13C and 207Pb nuclear magnetic resonance study of two triorganolead methoxides and a stabilized triorganolead cation

✍ Scribed by Bernd Wrackmeyer; Klaus Horchler; Angelika Sebald; Lawrence H. Merwin

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 513 KB
• Volume: 28
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260280515

✦ Synopsis

Abstract

Liquid‐ and solid‐state NMR data (^13^C, ^207^Pb) are reported for three organolead compounds, Me~3~PbOMe (1) and two comparable heterocycles, 5,5,4‐tricyclopentyl‐2,5‐dihydro‐1,2,2,3‐tetramethyl‐1,2,5‐oxoniaplumbaboratol (2) and (E)‐2‐dimethyl‐3‐diisopropyl(propinyl)borata‐4‐methyl‐2‐pentene (3); 2 contains a bridging methoxy group, and a triorganolead cation is stabilized by a bridging alkynyl group in 3. Compound 1 is shown to be associated in solution and forms chains in the solid state with bridging methoxy groups. The ^207^Pb CP‐MAS NMR spectrum of 1 shows that there is a single lead site with near‐axial symmetry. Two‐dimensional heteronuclear ^13^C/^1^H shift correlations were used to obtain the relative signs of numerous J(^207^Pb^13^C) and J(^207^Pb^1^H) coupling constants. In the case of 2 and 3 the ^1^J(^207^Pb^13^C~Me~) coupling constants have a negative sign. This indicates an extremely distorted tetrahedral surrounding of the lead atom. The isotropic ^207^Pb chemical shifts of 2 and 3 are almost identical in the solid state and in solution. Therefore, the structures in the solid state are fully retained in solution. Quantitative analysis of the spinning side‐band pattern of the ^207^Pb CP‐MAS spectra gave similar chemical shift anisotropies, Δσ(^207^Pb‐1133) ppm (2) and ‐1223 ppm (3), and also similar tensorial components of σ(^207^Pb), indicating that the basic structures of the two heterocyclic systems are comparable except for the bridging unit.