Stereochemically non-rigid silanes, germanes, and stannanes. Part 11. Mechanistic implications of diastereotopic effects induced in methylcyclopentadienyl, indenyl, and pentamethylcyclopentadienyl ring systems by chiral tin substituents
- 1 January 1982
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 11,p. 2275-2279
- https://doi.org/10.1039/dt9820002275
Abstract
The synthesis and characterization by 1H and 13C n.m.r. spectroscopy of the racemic, chiral cyclopentadienyl-related compounds Sn*MePriPh(R)[R = C5H4Me (2); R = C9H7(3); R = C5Me5(4)] is reported. For (2) and (4) the n.m.r. data are exclusively fast-limiting; compound (3) exhibits temperature-dependent behaviour. Diastereotopic effects in the isopropyl substituent identified by 1H [(2) and (3)] or l3C n.m.r. [compound (4)] establish that for each compound metallotropic rearrangement occurs with retention of configuration at tin. The dynamic process in (2) is discussed in terms of facile epimerization; slow-limiting data for (3) show the presence of two diastereoisomers which stereomutate at elevated temperature; the degenerate rearrangement of (4) is related to the behaviour of unsubstituted analogues and the Woodward–Hoffmann [1,5] sigmatropic shift.Keywords
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