Kinetics of Oxygen-Atom Transfer Reactions of α -[PMo 12 O 40 ] 3− and of A- β -[PMo 3 W 9 O 40 ] 3− Anion Salts with PPh 3 in Non-Aqueous Solution
1995; Oxford University Press; Volume: 68; Issue: 3 Linguagem: Inglês
10.1246/bcsj.68.838
ISSN1348-0634
AutoresIsao Kawafune, Gen‐etsu Matsubayashi,
Tópico(s)Chemical Synthesis and Reactions
ResumoThe kinetics of the oxygen-atom transfer reactions of α-[NBun4]3[PMo12O40] (abbreviated PMo12) and of A-β-[NBun4]3[PMo3W9O40] (abbreviated PMo3W9) with PPh3 were investigated in acetonitrile at 23—82 °C. Each reaction is first order in both the heteropolyanion salt and PPh3. The second-order rate constants at 23 °C are k2 = 6.53 × 10−4 and 4.58 × 10−5 (dm3 mol−1 s−1) for the reduction of PMo12 and PMo3W9, respectively. The difference in the k2 values is attributed to the number of active sites for oxygen transfer; PMo3W9 has only three corner-sharing oxygen atoms in the Mo(VI)–O–Mo (VI) bonds, whereas there are twelve corner-sharing and twelve edge-sharing oxygen atoms in PMo12. The activation parameters are, however, almost identical for both reactions: ΔH‡ = 43.6 and 43.4 (kJ mol−1) and ΔS‡ = −158 and −181 (J K−1 mol−1) for the reduction of PMo12 and PMo3W9, respectively. These results suggest a similar transition state in the oxygen-atom transfer reactions via the Mo–O–Mo sites of PMo12 and PMo3W9.
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