Synthesis and redox behaviour of the chalcogenocarbonyl dianions [(E)C(PPh(2)S)(2)](2-): formation and structures of chalcogen-chalcogen bonded dimers and a novel selone |
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| Authors: | Konu Jari Chivers Tristram Tuononen Heikki M |
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| Affiliation: | Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4, Canada. |
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| Abstract: | The lithium salts of the chalcogenocarbonyl dianions [(E)C(PPh2S)2]2? (E=S ( 4 b ), Se ( 4 c )) were produced through the reactions between Li2[C(PPh2S)2] and elemental chalcogens in the presence of tetramethylethylenediamine (TMEDA). The solid‐state structure of {[Li(TMEDA)]2[(Se)C(PPh2S)2]}—[{Li(TMEDA)}2 4 c ]—was shown to be bicyclic with the Li+ cations bis‐S,Se‐chelated by the dianionic ligand. One‐electron oxidation of the dianions 4 b and 4 c with iodine afforded the diamagnetic complexes {[Li(TMEDA)]2[(SPh2P)2CEEC(PPh2S)2]} ([Li(TMEDA)]2 7 b (E=S), [Li(TMEDA)]2 7 c (E=Se)), which are formally dimers of the radical anions [(E)C(PPh2S)2]? . (E=S ( 5 b ), Se ( 5 c )) with elongated central E? E bonds. Two‐electron oxidation of the selenium‐containing dianion 4 c with I2 yielded the LiI adduct of a neutral selone {[Li(TMEDA)][I(Se)C(PPh2S)2]}—[{LiI(TMEDA)} 6 c ]—whereas the analogous reaction with 4 b resulted in the formation of 7 b followed by protonation to give {[Li(TMEDA)][(SPh2P)2CSS(H)C(PPh2S)2]}—[Li(TMEDA)] 8 b . Attempts to identify the transient radicals 5 b and 5 c by EPR spectroscopy in conjunction with DFT calculations of the electronic structures of these paramagnetic species and their dimers are also described. The crystal structures of [{Li(TMEDA)}2 4 c ], [{LiI(TMEDA)} 6 c ] ? C7H8, [Li(TMEDA)]2 7 b? (CH2Cl2)0.33, [Li(THF)2]2 7 b , [Li(TMEDA)]2 7 c , [Li(TMEDA)] 8 b? (CH2Cl2)2 and [Li([12]crown‐4)2] 8 b were determined and salient structural features are discussed. |
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| Keywords: | chalcogens electronic structure oxidation radicals tridentate ligands |
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