10.1021/acs.organomet.8b00759.s001 Pei-Hua Zhao Pei-Hua Zhao Meng-Yuan Hu Meng-Yuan Hu Jian-Rong Li Jian-Rong Li Zhong-Yi Ma Zhong-Yi Ma Yan-Zhong Wang Yan-Zhong Wang Jiao He Jiao He Yu-Long Li Yu-Long Li Xu-Feng Liu Xu-Feng Liu Influence of Dithiolate Bridges on the Structures and Electrocatalytic Performance of Small Bite-Angle PNP-Chelated Diiron Complexes Fe<sub>2</sub>(μ-xdt)(CO)<sub>4</sub>{κ<sup>2</sup>‑(Ph<sub>2</sub>P)<sub>2</sub>NR} Related to [FeFe]-Hydrogenases American Chemical Society 2019 2 NR diiron FT-IR 3 NMe 2 xdt Fe 2 S 2 complexes complexes 1 b UV CH 2 SCH 2 CH 2 S NMR Ph 2 P edt complexes 2 chelating PNP ligands adt NPh CH 2 CHMe 2 single-crystal X-ray diffraction analysis carbonyl substitution reactions adt NPh complexes 1 2019-01-03 20:04:50 Journal contribution https://acs.figshare.com/articles/journal_contribution/Influence_of_Dithiolate_Bridges_on_the_Structures_and_Electrocatalytic_Performance_of_Small_Bite-Angle_PNP-Chelated_Diiron_Complexes_Fe_sub_2_sub_-xdt_CO_sub_4_sub_sup_2_sup_Ph_sub_2_sub_P_sub_2_sub_NR_Related_to_FeFe_-Hydrogenases/7544861 As a further exploration of the asymmetrically substituted diiron models for the active site of [FeFe]-hydrogenases, two new types of small bite-angle aminodiphosphine [(Ph<sub>2</sub>P)<sub>2</sub>NR; denoted as PNP in this study]-chelated diiron <i>N</i>-phenyl-aza- and ethanedithioate complexes Fe<sub>2</sub>(μ-xdt)­(CO)<sub>4</sub>{κ<sup>2</sup>-(Ph<sub>2</sub>P)<sub>2</sub>NR} (<b>1a</b>–<b>1e</b>) and (<b>2a</b>–<b>2e</b>), respectively, were successfully synthesized by the carbonyl substitution reactions of all-carbonyl diiron complexes Fe<sub>2</sub>(μ-xdt)­(CO)<sub>6</sub> (xdt = SCH<sub>2</sub>N­(Ph)­CH<sub>2</sub>S (adt<sup>NPh</sup>) and SCH<sub>2</sub>CH<sub>2</sub>S (edt)) with PNP (PNP = (Ph<sub>2</sub>P)<sub>2</sub>NR, R = CMe<sub>3</sub>, CH<sub>2</sub>CHMe<sub>2</sub>, (CH<sub>2</sub>)<sub>3</sub>Me, (CH<sub>2</sub>)<sub>3</sub>Si­(OEt)<sub>3</sub>, and (CH<sub>2</sub>)<sub>3</sub>NMe<sub>2</sub>) in the presence of Me<sub>3</sub>NO·2H<sub>2</sub>O or UV irradiation. All the new complexes obtained above have been well characterized by elemental analysis, FT-IR, NMR spectroscopy, and particularly for <b>1a</b>, <b>1b</b>, <b>2a</b>, and <b>2d</b> by single-crystal X-ray diffraction analysis. By comparison, <sup>31</sup>P­{<sup>1</sup>H} NMR and X-ray crystallographic studies have clearly revealed that the change of the dithiolate bridge from adt<sup>NPh</sup> to edt has a significant influence on the coordination geometry of the chelating PNP ligands in Fe<sub>2</sub>S<sub>2</sub> complexes, in which the basal–basal configuration in the adt<sup>NPh</sup> complexes <b>1a</b>–<b>1e</b> is favorable whereas the apical–basal conformation in the edt complexes <b>2a</b>–<b>2e</b> is main. In addition, the electrochemical properties of complexes <b>1b</b> and <b>2b</b> as a pair of representative counterparts are evaluated and compared by cyclic voltammetry in the absence and presence of HOAc as a proton source, indicating that they are found to be electrocatalytically active.