Comparison of two Mn^IVMn^IV-bis-μ-oxo complexes {[Mn^IV(N₄(6-Me-DPEN))]₂(μ-O)₂}²⁺ and {[Mn^IV(N₄(6-Me-DPPN))]₂(μ-O)₂}²⁺

Abstract

<jats:p>The addition of <jats:italic>tert</jats:italic>-butyl hydroperoxide (<jats:sup> <jats:italic>t</jats:italic> </jats:sup>BuOOH) to two structurally related Mn<jats:sup>II</jats:sup> complexes containing <jats:italic>N,N</jats:italic>-bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me-DPEN) and <jats:italic>N,N</jats:italic>-bis(6-methyl-2-pyridylmethyl)propane-1,2-diamine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis{[<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>-bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine]manganese(II)}(<jats:italic>Mn</jats:italic>—<jats:italic>Mn</jats:italic>) bis(tetraphenylborate) dihydrate, [Mn(C<jats:sub>16</jats:sub>H<jats:sub>22</jats:sub>N<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>](C<jats:sub>24</jats:sub>H<jats:sub>20</jats:sub>B)<jats:sub>2</jats:sub>·2H<jats:sub>2</jats:sub>O or {[Mn<jats:sup>IV</jats:sup>(N<jats:sub>4</jats:sub>(6-Me-DPEN))]<jats:sub>2</jats:sub>(<jats:italic>μ</jats:italic>-O)<jats:sub>2</jats:sub>}(2BPh<jats:sub>4</jats:sub>)(2H<jats:sub>2</jats:sub>O) (<jats:bold>1</jats:bold>) and di-μ-oxido-bis{[<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>-bis(6-methyl-2-pyridylmethyl)propane-1,3-diamine]manganese(II)}(<jats:italic>Mn</jats:italic>—<jats:italic>Mn</jats:italic>) bis(tetraphenylborate) diethyl ether disolvate, [Mn(C<jats:sub>17</jats:sub>H<jats:sub>24</jats:sub>N<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>](C<jats:sub>24</jats:sub>H<jats:sub>20</jats:sub>B)<jats:sub>2</jats:sub>·2C<jats:sub>4</jats:sub>H<jats:sub>10</jats:sub>O or {[Mn<jats:sup>IV</jats:sup>(N<jats:sub>4</jats:sub>(6-MeDPPN))]<jats:sub>2</jats:sub>(<jats:italic>μ</jats:italic>-O)<jats:sub>2</jats:sub>}(2BPh<jats:sub>4</jats:sub>)(2Et<jats:sub>2</jats:sub>O) (<jats:bold>2</jats:bold>). Complexes <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold> both contain the `diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of <jats:bold>2</jats:bold>, as compared to that of the ethyl linker in <jats:bold>1</jats:bold>, results in more elongated Mn—N bonds, as one would expect. The Mn—Mn distances and Mn—O bond lengths support an Mn<jats:sup>IV</jats:sup> oxidation state assignment for the Mn ions in both <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold>. The angles around the Mn centers are consistent with the local pseudo-octahedral geometry.</jats:p>

Synthesis, structural and physicochemical properties of a series of manganese(II) complexes with a novel N5 tripodal-amidate ligand and their potential use as water oxidation catalysts

“…Apparently, the metal centred reversible redox processes of complexes 1 -3 are of 2eand were assigned to Mn II -Mn IV redox couple. At this point, it is worth noting that mononuclear or multinuclear manganese(IV) compounds are stabilized by either ligands containing nitrogen donor atoms [37][38][39][40] or ligands with mixed nitrogen and oxygen donor atoms [41]. Based on Hard-Soft Acid-Base (HSAB) theory someone expects harder donor atoms such as oxygen donor atoms to stabilize better Mn IV , which is a hard acid, than nitrogen donor atoms.…”

Influence of Thiolate versus Alkoxide Ligands on the Stability of Crystallographically Characterized Mn(III)-Alkylperoxo Complexes

“…In contrast to 7 (Figure 2), no intermediates are observed in the reaction between t BuOOH and five-coordinate 5. Instead, direct conversion to a stable, crystallographically characterized bis-oxo-bridged Mn(IV)Mn(IV) dimer is observed, 51 implying that the rate-determining step involves t BuOOH binding to 5. The final product in the reaction between 7 and t BuOOH is also a bis-oxo Mn(IV)Mn(IV) dimer.…”