Department of Chemistry, University of California , Irvine, California 92697, United States.
J Am Chem Soc. 2015 Nov 11;137(44):14114-21. doi: 10.1021/jacs.5b07777. Epub 2015 Nov 2.
The free energy of hydride donation (hydricity) for [HNi(DHMPE)2][BF4] (DHMPE = 1,2-bis(dihydroxymethylphosphino)ethane was experimentally determined versus the heterolytic cleavage energy of hydrogen in acetonitrile, dimethyl sulfoxide, and water to be 57.4, 55.5, and 30.0 kcal/mol, respectively. This work represents the first reported hydricity values for a transition metal hydride donor in three different solvents. A comparison between our values and the hydricity of hydrogen and formate reveals a narrowing in the range of values with increasing solvent polarity. The thermochemical values also reveal solvation effects that impact the overall thermodynamic favorability of hydride generation from hydrogen and transfer to carbon dioxide. The quantitative solvation effects described herein have important consequences to the design and reactivity of catalysts for transformations that have hydride transfer steps throughout synthetic chemistry.
实验测定了[HNi(DHMPE)2][BF4]（DHMPE=1,2-双（二羟甲基膦基）乙烷）中氢化物供体的游离能（氢化物供体）相对于在乙腈、二甲亚砜和水中氢的异裂能分别为 57.4、55.5 和 30.0 kcal/mol。这项工作代表了在三种不同溶剂中首次报道的过渡金属氢化物供体的氢化物供体值。将我们的值与氢和甲酸盐的氢化物供体值进行比较，可以发现随着溶剂极性的增加，值的范围变窄。热化学值还揭示了溶剂化效应，这些效应影响了从氢生成氢化物并转移到二氧化碳的整体热力学有利性。本文所述的定量溶剂化效应对整个合成化学中具有氢化物转移步骤的转化催化剂的设计和反应性具有重要意义。
