Alkoxide Migration at a Nickel(II) Center Induced by a π-Acidic Ligand: Migratory Insertion versus Metal–Ligand Cooperation

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• 作者：Seohee Oh ; Seji Kim ; Dayoung Lee ; Jinseong Gwak ; Yunho Lee
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：December 19, 2016
• 年：2016
• 卷：55
• 期：24
• 页码：12863-12871
• 全文大小：419K
• ISSN：1520-510X

文摘

Two pathways of alkoxide migration occurring at a nickel(II) center supported by a PPP ligand (PPP⁻ = P[2-PⁱPr₂-C₆H₄]₂^–) are presented in this Article. In the first route, the addition of a π-acidic ligand to a (PPP)Ni alkoxide species reveals the formation of a P–O bond. This reaction occurs via metal–ligand cooperation (MLC) involving a 2-electron reduction at nickel. To demonstrate a P–O bond formation, a nickel(II) isopropoxide species (PPP)Ni(OⁱPr) (4) was prepared. Upon addition of a π-acidic isocyanide ligand CN^tBu, a nickel(0) isocyanide species (PP^OiPrP)Ni(CN^tBu) (6b) was generated; P–O bond formation occurred via reductive elimination (RE). When CO is present, migratory insertion (MI) occurs instead. The reaction of 4 with CO(g) results in the formation of (PPP)Ni(COOⁱPr) (5), representing an alternative pathway. The corresponding RE product (PP^OiPrP)Ni(CO) (6a) can be independently produced from the substitution reaction of {(PP^OiPrP)Ni}₂(μ-N₂) (3) with CO(g). While two different carbonylation pathways in 4 seem feasible, C–O bond forming migratory insertion singly occurs. Regeneration of a (PPP)Ni moiety via a P–O bond cleavage was demonstrated by treating 3 with CO₂(g). The formation of (PPP)Ni(OCOOⁱPr) (7) clearly shows that an isopropoxide group migrates onto the bound CO₂ ligand, and a P–Ni moiety is regenerated.