Electronic aspects of the phosphine-oxide聽鈫捖爌hosphinous acid tautomerism and the assisting role of transition metal centers

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• 作者：Gabriele Manca ; Maria Caporali ; Andrea Ienco ; Maurizio Peruzzini ; ^{maurizio.peruzzini@iccom.cnr.it" class="auth_mail} ; Carlo Mealli ; ^{mealli@iccom.cnr.it" class="auth_mail} ; ^{carlomealli@gmail.com" class="auth_mail}
• 关键词：Phosphine oxide ; Phosphinous acid ; Tautomerization ; Ruthenium ; Water chemistry ; DFT mechanistic studies
• 刊名：Journal of Organometallic Chemistry
• 出版年：15 June, 2014
• 年：2014
• 卷：760
• 期：Complete
• 页码：177-185
• 全文大小：1616 K

文摘

The H₃P(O)聽鈫捖燞₂P(OH) tautomerism is addressed by experimental and DFT approaches. The process, disfavored for the free molecule, is easier over metal fragments of the type {CpRu^IIL₂}ⁿ (L聽=聽uncharged or anionic phosphine ligand), with an energy barrier reduced to one fourth. The free H₃P(O) molecule is a very weak acid and hardly a proton migrates intra-molecularly towards the oxo atom, as expected for classic acid-base reactions. Rather, some electron density of the highly covalent P-H bond remains anchored to the H atom at least up to the TS with the barrier originated from the electronic repulsion with the approached O lone pair. Beyond TS, the H atom transforms into a proton after having released its electron portion at the P atom (lone pair). The calculations show the experimentally undetected intermediate [CpRu(PR₃)₂(H)(H₂PO)]ⁿ, at which the metal has induced a P-H oxidative addition. Consistent behaviors are found for all the molecules H_n(OH)_3鈭?em>nP(O) (n聽=聽3, 2, 1), whereas some anomalies have been experimentally observed with the anionic TPPMS coligands [TPPMS聽=聽PPh₂(m-C₆H₄SO₃)^{鈭?/sup>], used to favor the chemistry in water. In particular: i) the reaction with H₃P(O) indicates that the product [CpRu(TPPMS)₂{H₂P(OH)}]鈭?/sup> exists in two isomeric forms; ii) the tautomerization of H(OH)₂P(O) is uniquely inhibited. Ad-hoc DFT calculations indicate that the features are attributable to the strong H-bonding networks between the sulphonate substituent and OH group(s) and water as well.}