10.1021/ic061570o.s003 John D. Gilbertson John D. Gilbertson Nathaniel K. Szymczak Nathaniel K. Szymczak Justin L. Crossland Justin L. Crossland Warren K. Miller Warren K. Miller David K. Lyon David K. Lyon Bruce M. Foxman Bruce M. Foxman Joclyn Davis Joclyn Davis David R. Tyler David R. Tyler Coordination Chemistry of H<sub>2</sub> and N<sub>2</sub> in Aqueous Solution. Reactivity and Mechanistic Studies Using <i>trans</i>-Fe<sup>II</sup>(P<sub>2</sub>)<sub>2</sub>X<sub>2</sub>-Type Complexes (P<sub>2</sub> = a Chelating, Water-Solubilizing Phosphine) American Chemical Society 2007 2O H 2 molecule N 2 chloride ligand pressure swing scheme crystal structure report homoleptic tris chelate H 2 H 2 ligand Fe nonaqueous solvents CH bidentate phosphine ligands DMeOPrPE ligand III II 2007-02-19 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Coordination_Chemistry_of_H_sub_2_sub_and_N_sub_2_sub_in_Aqueous_Solution_Reactivity_and_Mechanistic_Studies_Using_i_trans_i_Fe_sup_II_sup_P_sub_2_sub_sub_2_sub_X_sub_2_sub_Type_Complexes_P_sub_2_sub_a_Chelating_Water_Solubilizing_Phosphine_/3025537 The reactions of the <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>Cl<sub>2</sub> complex (<b>I</b>; DMeOPrPE = 1,2-bis(bis(methoxypropyl)phosphino)ethane) and its derivatives were studied in aqueous and nonaqueous solvents with a particular emphasis on the binding and activation of H<sub>2</sub> and N<sub>2</sub>. The results show there are distinct differences in the reaction pathways between aqueous and nonaqueous solvents. In water, <b>I</b> immediately reacts to form <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>O)Cl<sup>+</sup>. Subsequent reaction with H<sub>2</sub> or N<sub>2</sub> yields <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(X<sub>2</sub>)Cl<sup>+</sup> (X<sub>2</sub>H<sub>2</sub> or N<sub>2</sub>). In the case of H<sub>2</sub>, further reactivity occurs to ultimately give the <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>)H<sup>+</sup> product (<b>III</b>). The pathway for the reaction <b>I</b> → <b>III</b> was spectroscopically examined:  following the initial loss of chloride and replacement with H<sub>2</sub>, heterolysis of the H<sub>2</sub> ligand occurs to form Fe(DMeOPrPE)<sub>2</sub>(H)Cl; substitution of the remaining chloride ligand by another H<sub>2</sub> molecule then occurs to produce <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>)H<sup>+</sup>. In the absence of H<sub>2</sub> or N<sub>2</sub>, <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>O)Cl<sup>+</sup> slowly reacts in water to form Fe(DMeOPrPE)<sub>3</sub><sup>2+</sup>, <b>II</b>. Experiments showed that this species forms by reaction of free DMeOPrPE ligand with <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>O)Cl<sup>+</sup>, where the free DMeOPrPE ligand comes from dissociation from the <i>trans</i>-Fe(DMeOPrPE)<sub>2</sub>(H<sub>2</sub>O)Cl<sup>+</sup> complex. In nonaqueous solvents, the chloride ligand in <b>I</b> is not labile, and a reaction with H<sub>2</sub> only occurs if a chloride abstracting reagent is present. Complex <b>III</b> is a useful synthon for the formation of other water-soluble metal hydrides. For example, the <i>trans</i>-[Fe(DMeOPrPE)<sub>2</sub>H(N<sub>2</sub>)]<sup>+</sup> complex was generated in H<sub>2</sub>O by substitution of N<sub>2</sub> for the H<sub>2</sub> ligand in <b>III</b>. The <i>trans</i>-Fe(DHBuPE)<sub>2</sub>HCl complex (DHBuPE = 1,2-bis(bis(hydroxybutyl)phosphino)ethane, another water-solubilizing phosphine) was shown to be a viable absorbent for the separation of N<sub>2</sub> from CH<sub>4</sub> in a pressure swing scheme. X-ray crystallographic analysis of <b>II</b> is the first crystal structure report of a homoleptic tris chelate of Fe<sup>II</sup> containing bidentate phosphine ligands. The structure reveals severe steric crowding at the Fe center.