Structure of the SO2F- Anion, a Problem Case

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• 作者：Enno Lork ; R&uuml ; diger Mews ; Detlef Viets ; Paul G. Watson ; Tobias Borrmann ; Ashwani Vij ; Jerry A. Boatz ; and Karl O. Christe
• 刊名：Inorganic Chemistry
• 出版年：2001
• 出版时间：March 12, 2001
• 年：2001
• 卷：40
• 期：6
• 页码：1303 - 1311
• 全文大小：122K
• 年卷期：v.40,no.6(March 12, 2001)
• ISSN：1520-510X

文摘

Recently, room-temperature crystal structures of SO₂F^- in its K⁺ and Rb⁺ salts were published in Z. Anorg. Allg.Chem. 1999, 625, 385 and claimed to represent the first reliable geometries for SO₂F^-. However, their almostidentical S-O and S-F bond lengths and O-S-O and O-S-F bond angles are in sharp contrast to the resultsfrom theoretical calculations. To clarify this discrepancy, the new [(CH₃)₂N]₃SO⁺ and the known [N(CH₃)₄⁺],[(CH₃)₂N]₃S⁺, and K⁺ salts of SO₂F^- were prepared and their crystal structures studied at low temperatures.Furthermore, the results from previous RHF and MP2 calculations were confirmed at the RHF, B3LYP, andCCSD(T) levels of theory using different basis sets. It is shown that all the SO₂F^- salts studied so far exhibitvarying degrees of oxygen/fluorine and, in some cases, oxygen-site disorders, with [(CH₃)₂N]₃SO⁺SO₂F^- at 113K showing the least disorder with r(S-F) - r(S-O) = 17 pm and ges/entities/ang.gif">(O-S-O) - ges/entities/ang.gif">(F-S-O) = 6ges/entities/deg.gif">. Refinementof the disorder occupancy factors and extrapolation of the observed bond distances for zero disorder resulted ina geometry very close to that predicted by theory. The correctness of the theoretical predictions for SO₂F^- isfurther supported by the good agreement between the calculated and the experimentally observed vibrationalfrequencies and their comparison with those of isoelectronic ClO₂F. A normal coordinate analysis of SO₂F^-confirms the weakness of the S-F bond with a stretching force constant of only 1.63 mdyn/Å and shows thatthere is no highly characteristic S-F stretching mode. The S-F stretch strongly couples with the SO₂ deformationmodes and is concentrated in the two lowest a' frequencies.