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Synthesis, characterization, protonation studies and X-ray crystal structure of ReH5(PPh3)2(PTA) (PTA = 1,3,5-triaza-7-phosphaadamantane) |
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| Authors: | Sandra Bolaño Luca Gonsalvi Alberto Albinati Evgenii Gutsul Lina Epstein Maurizio Peruzzini |
| Institution: | a Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy b Dipartimento di Chimica Strutturale, Università di Milano, Via G. Venezian 21, 20133 Milano, Italy c Institute of Organoelement Compounds, INEOS RAS, Vavilova str 28, 119991 Moscow, Russia |
| Abstract: | The novel rhenium pentahydride complex ReH5(PPh3)2(PTA)] (2) was synthesized by dihydrogen replacement from the reaction of ReH7(PPh3)2] with PTA in refluxing THF. Variable temperature NMR studies indicate that 2 is a classic polyhydride (T1(min) = 133 ms). This result agrees with the structure of 2, determined by X-ray crystallography at low temperature. The compound shows high conformational rigidity which allows for the investigation of the various hydride-exchanging processes by NMR methods. Reactions of 2 with equimolecular amounts of either HFIP or HBF4 · Et2O at 183 K afford ReH5(PPh3)2{PTA(H)}]+ (3) via protonation of one of the nitrogen atoms on the PTA ligand. When 5 equivalents of HBF4 · Et2O are used, additional protonation of one hydride ligand takes place to generate the thermally unstable dication ReH4(η2-H2)(PPh3)2{PTA(H)}]2+ (4), as confirmed by 1H NMR and T1 analysis. IR monitoring of the reaction between 2 and CF3COOD at low temperature shows the formation of the hydrogen bonded complex ReH5(PPh3)2{PTA?DOC(O)CF3}] (5) and of the ionic pair ReH5(PPh3)2{PTA(D)?OC(O)CF3}] (6) preceding the proton transfer step leading to 3. |
| Keywords: | Rhenium Hydrides X-ray crystallography Hydrogen bonding IR and NMR spectroscopy |
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