Synthesis and Reactivity of Nickel and Palladium Fluoride Complexes with PCP Pincer Ligands. NMR-Based Assessment of Electron-Donating Properties of Fluoride and Other Monoanionic Ligands

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• 作者：Luis Miguel Martı ; ́ ; nez-Prieto ; Crist贸bal Melero ; Diego del Rı ; ́ ; o ; Pilar Palma ; Juan C谩mpora ; Eleuterio 脕lvarez
• 刊名：Organometallics
• 出版年：2012
• 出版时间：February 27, 2012
• 年：2012
• 卷：31
• 期：4
• 页码：1425-1438
• 全文大小：626K
• 年卷期：v.31,no.4(February 27, 2012)
• ISSN：1520-6041

文摘

A series of complexes of the type [(^iPrPCP)M-L] (M = Ni, Pd), containing the 2,6-bis(diisopropylphosphinomethyl)phenyl (^iPrPCP) pincer ligand and simple monoanionic ligands L (F, Cl, Br, H, Me, Ph, NO₃, and OTf), have been synthesized and characterized. The fluoride derivatives [(^iPrPCP)M-F] were prepared from the halides [(^iPrPCP)M-X] (M = Ni, X = Br; M = Pd, X = I) by exchange reactions with AgF or, alternatively, by protonolysis of the methyl complexes [(^iPrPCP)M-Me] with Et₃N路3HF (TREAT-HF). A survey of the ¹³C NMR data for the new complexes and previously reported ones with L = OH, OMe, and NH₂ revealed significant trends that can be directly related to the electronic properties of the anionic ligands L coordinated to Ni(II) and Pd(II) centers. The chemical shift of the ¹³C resonance of the metal-bound ipso carbon is very sensitive to the 蟽-donating capacity of L, which increases in the order L = OTf > NO₃ > F > OAc > OMe > Cl > OH 鈮?Br > I > NH₂ > Ph > Me > H. In addition, the reactivity of [(^iPrPCP)M-F] complexes was investigated. These readily undergo fluoride exchange with LiOMe, affording the corresponding methoxides [(^iPrPCP)M-OMe] and LiF. They also react with n-C₁₂H₁₃I to cleanly yield [(^iPrPCP)M-I] and n-C₁₂H₁₃F. Comparison of the rates of the latter reactions and analogous ones involving bromide or chloride complexes showed that the fluorides are significantly more nucleophilic, particularly the palladium derivative. This property was applied in a palladium-catalyzed reaction for the synthesis of alkyl fluorides using AgF as the fluoride source.