Kinetic studies on the reactions of tricarbonyl(η-cyclo-octa-1,3-diene)-, tricarbonyl(η-cyclohexa-1,3-diene)-, and tricarbonyl(η-cyclohepta-1,3,5-triene)-iron complexes with triphenylphosphine
- 1 January 1974
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 23,p. 2546-2549
- https://doi.org/10.1039/dt9740002546
Abstract
Tricarbonyl(η-cycle-octa-1,3-diene) iron reacts smoothly with excess of triphenylphosphine via a second-order process to form trans-[Fe(CO)3(PPh3)2]. At 60 °C in n-heptane: k2=(3·15 ± 0·08)× 10–3 l mol–1 s–1, ΔH‡= 20·76 ± 0·22 kcal mol–1, and ΔS‡=–8·0 ± 0·6 cal K–1 mol–1. In contrast, tricarbonyl (η-cyclohepta-1,3-diene)iron and tricarbonyl(η-cyclohexa-1,3-diene)iron do not react with triphenylphosphine under these conditions. The last complex undergoes a CO-dissociative reaction at high temperatures (ΔH‡= 42·1 ± 0·8 kcal mol–1 and ΔS‡= 16·5 ± 1·8 cal K–1 mol–1) with retention of the olefin. Tricarbonyl(η-cyclohepta-1,3,5-triene)iron is similarly unreactive, but its reaction with triphenylphosphine at 154 °C involves both first- and second-order processes.Keywords
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