The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptors

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• 作者：Dan A. Smith ; Torsten Beweries ; Clemens Blasius ; Naseralla Jasim ; Ruqia Nazir ; Sadia Nazir ; Craig C. Robertson ; Adrian C. Whitwood ; Christopher A. Hunter ; Lee Brammer ; Robin N. Perutz
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：September 16, 2015
• 年：2015
• 卷：137
• 期：36
• 页码：11820-11831
• 全文大小：652K
• ISSN：1520-5126

文摘

The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C₅NF₄)(PR₃)₂], R = Et 1a, Cy 1b, trans-[Pd(F)(4-C₅NF₄)(PCy₃)₂] 2, trans-[Pt(F){2-C₅NF₂H(CF₃)}(PCy₃)₂] 3 and of group 4 difluorides (Cp₂MF₂, M = Ti 4a, Zr 5a, Hf 6a; Cp*₂MF₂, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability 尾 (Hunter scale) for the group 10 metal fluorides is far greater (1a 12.1, 1b 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, 5a 4.7, 6a 4.7, 4b 6.9, 5b 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me₃NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to 1a in carbon tetrachloride (鈭?3.5 卤 0.3 kJ mol^鈥?) interlocks our study with Laurence鈥檚 scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of p蟺鈥揹蟺 bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C₅NF₃(NH₂)}(PEt₃)₂], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.