Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo-Protonation Sites
Electrocatalytic Hydrogen Production by [Ni(7PPh2NH)2]2+: Removing the Distinction Between Endo- and Exo-Protonation Sites
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DOI：
10.1021/cs502132y
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发表时间：
2015-04
期刊：
影响因子：
12.9
通讯作者：
H. Brown;Stefan Wiese;John A. S. Roberts;R. Bullock;Monte L. Helm
中科院分区：
文献类型：
--
作者：
H. Brown;Stefan Wiese;John A. S. Roberts;R. Bullock;Monte L. Helm
合成了一种新的Ni（II）配合物[Ni（7 PPh 2NH）2 H]3+（7 PPh 2NH = 3，6-二苯基-1-氮杂-3，6-二磷杂环庚烷），并研究了其电化学性质。7 PPh 2NH配体具有NH，确保适当定位的质子化胺基（N-H+）用于电催化，无论质子化是发生在金属中心的外或内。该化合物是在有机酸存在下生产H2的电催化剂（在CH 3CN中pKa范围为10-13），在320和470 mV之间的过电位下，在催化波电位下测量的转换频率范围为160至780 s-1。与[Ni（7 PPh 2NR ′2）2]2+（PPh 2NR ′2 = 3，7-二苯基-1，5-二氮杂-3，7-二磷杂环辛烷）和其他[Ni（7 PPh 2NR ′）2]2+配合物形成鲜明对比的是，[Ni（7 PPh 2NH）2]2+对H2生产的催化转换频率在加入H2O后没有显示出催化速率增强。这一发现支持了[Ni（7 PPh 2NH）2]2+消除了内质子和外质子之间的区别的论断。
A new Ni(II) complex, [Ni(7PPh2NH)2H]3+ (7PPh2NH = 3,6-diphenyl-1-aza-3,6-diphosphacycloheptane), has been synthesized, and its electrochemical properties have been reported. The 7PPh2NH ligand features an NH, ensuring properly positioned protonated amine groups (N–H+) for electrocatalysis, regardless of whether protonation occurs exo or endo to the metal center. The compound is an electrocatalyst for H2 production in the presence of organic acids (pKa range 10–13 in CH3CN), with turnover frequencies ranging from 160 to 780 s–1 at overpotentials between 320 and 470 mV, as measured at the potential of the catalytic wave. In stark contrast to [Ni(PPh2NR′2)2]2+ (PPh2NR′2 = 3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) and other [Ni(7PPh2NR′)2]2+ complexes, catalytic turnover frequencies for H2 production by [Ni(7PPh2NH)2]2+ do not show catalytic rate enhancement upon the addition of H2O. This finding supports the assertion that [Ni(7PPh2NH)2]2+ eliminates the distinction between the endo- and exo-protonat...