Chelate ring-closure kinetics of Cr(CO)5 (DPPM) studied by 31P-NMR spectroscopy

1996-12-01
Özkar, Saim
Kayran, Ceyhan
Tekkaya, Ayşin
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31 P-NMR spectroscopy was used to study the kinetics of the chelate ring-closure reaction in Cr(CO) 5 (DPPM) where DPPM is bis (diphenylphosphino)methane. DPPM is potentially a bidentate ligand, but in this complex it is coordinated to the transition metal in a monodentate fashion and therefore can undergo chelation. The thermal chelate ring-closure reaction was carried out in an NMR sample tube at a constant temperature and the course of the reaction was quantitatively followed by taking31 P-NMR spectra in appropriate time intervals. Kinetic results have shown that the chelate ring-closure reaction of Cr(CO)5 DPPM is of zero-order. Activation parameters were determined by evaluating the kinetic data. The large negative value of the activation entropy implies that the mechanism of the chelate ring-closure reaction is of associative nature in the transition states. The rate determining step might involve both Cr-CO bond breaking and Cr-P bond making. This will generate a seven coordinate transient complex from which the complete detachment of a CO ligand will lead to the formation of Cr(CO)4 (DPPM).
https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030304102&origin=inward
https://hdl.handle.net/11511/102721
https://journals.tubitak.gov.tr/cgi/viewcontent.cgi?article=3280&context=chem
Turkish Journal of Chemistry
Graduate School of Natural and Applied Sciences, Article

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Citation Formats
S. Özkar, C. Kayran, and A. Tekkaya, “Chelate ring-closure kinetics of Cr(CO)5 (DPPM) studied by 31P-NMR spectroscopy,” Turkish Journal of Chemistry, vol. 20, no. 1, pp. 74–79, 1996, Accessed: 00, 2023. [Online]. Available: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030304102&origin=inward.
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