Solid-state (CP-MAS) 29Si-, 119Sn and 207Pb nuclear magnetic resonance study of bis(pentamethylcyclopentadienyl)-silicon, -tin and -lead

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

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 397 KB
• Volume: 29
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260290311

✦ Synopsis

Abstract

Solid‐state CP‐MAS ^29^Si‐, ^119^Sn‐ and ^207^Pb NMR spectra of bis(pentamethylcyclopentadienyl)‐silicon (1) ‐tin (2) and ‐lead (3) were measured. The spectra reflect the gross structural features, known from x‐ray analyses for 1–3. In 1a, which has a parallel arrangement of the Me~5~C~5~ rings, the ^29^Si nuclear shielding is found to be 20.2 ppm higher than that of the bent structure in 1b. The assignment is supported by the relative intensities of the ^29^Si resonances and by the analyses of the spinning sideband patterns. The δ^29^Si value of 1 in solution is close to that of 1b, suggesting that the bent structure is preferred in solution. The comparison of the solution‐ and solid‐state δ values shows that the η^5^‐bonding of the cyclopentadienyl rings is retained in solution. Attempts to analyse the spinning sideband pattern of 2 by the usual methods failed, which may be explained by the presence of molecular reorientation in the solid state which occurs at room temperature at a rate affecting the ^119^Sn shielding tensor.