Osmium Phosphiniminato Complexes: Synthesis, Protonation, Structure, and Redox-Coupled Hydrolytic Scission of N-P Bonds

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• 作者：Brian K. Bennett ; Erik Saganic ; Scott Lovell ; Werner Kaminsky ; Amanda Samuel ; and James M. Mayer
• 刊名：Inorganic Chemistry
• 出版年：2003
• 出版时间：June 30, 2003
• 年：2003
• 卷：42
• 期：13
• 页码：4127 - 4134
• 全文大小：151K
• 年卷期：v.42,no.13(June 30, 2003)
• ISSN：1520-510X

文摘

The osmium(VI) nitrido complex TpOs(N)Cl₂ [1, Tp = hydrotris(1-pyrazolyl)borate] reacts with triarylphosphines toafford the Os^IV phosphiniminato complexes TpOs(NPAr₃)Cl₂ [Ar = p-tolyl (tol) (2a), phenyl (2b), p-CF₃C₆H₄ (2c)]in nearly quantitative yield. Protonation of 2a-c with 1 equiv of HOTf in MeCN occurs at the phosphiniminatonitrogen to give [TpOs^IV(NHPAr₃)Cl₂]OTf (3a-c) in 68-80% yield. Solutions of 2a-c in CH₂Cl₂ react with excessH₂O over 1 week to form the disproportionation products 1 (28%), TpOs^III(NHPAr₃)Cl₂ (4a-c) (60%), and OPAr₃(35%). Treatment of solutions of 3a-c with H₂O also affords 1, 4a-c, and OPAr₃. X-ray structures of 2b, 3b, and4b are presented. Cyclic voltammograms of compounds 2a-c exhibit Os^V/Os^IV and Os^IV/Os^III couples at ~0.3 and-1 V versus Cp₂Fe^+/0. Protonation to give 3 makes reduction easier by ~1.2 V, so that these compounds showOs^IV/Os^III and Os^III/Os^II couples. In the hydrolytic disproportionation of 2a-c, labeling studies using ¹⁸O-enriched O₂and H₂O establish water as the source of the oxygen atom in the OPAr₃ product. The conversions are acceleratedby HOTf and inhibited by NaOD. The relative rates of hydrolytic disproportionation of 2a-c vary in the order tol >Ph > p-CF₃C₆H₄. The data indicate that protonation of the phosphiniminato nitrogen is required for hydrolysis. Themechanism of the hydrolytic disproportionation is compared to that of the related reaction of the osmium(IV) acetonitrilecomplex [TpOs(NCMe)Cl₂]⁺.