ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
In chloroform, [ZrCl4·2(MeO)3PO] exists in both cis- and trans-isomeric forms. Three reactions can be envisaged in the presence of excess (MeO)3PO = L: (1) cis-[ZrCl4·2L] + *L⇆cis-[ZrCl4·L*L]+ L; (2) trans-[ZrCl4·2L] + *L ⇆ trans-[ZrCl4·L*L] + L; (3) cis-[ZrCl4·2L]⇆ trans-[ZrCl4·2L]. To distinguish between these possible reaction pathways, we have used 2D 1H-NMR spectroscopy. For the first time, variable-pressure 2D exchange spectra were used for mechanistic assignments. cis/trans-Isomerisation was found to be the fastest reaction (in CHCl3/CDCl3), with a small acceleration at higher pressure: it is concluded to be an intramolecular process with a slightly contracted six-coordinate transition state. The intermolecular (MeO)3PO exchange on the cis- and trans-isomer are second-order processes and are strongly accelerated by increased pressure: Ia mechanisms are suggested without ruling out limiting A mechanisms.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19900730123
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