Versatile Reactivity of CH₃CN‐Coordinated Nickel‐Iron Heterodimetallic Complexes with Cp* Ligand on Diazadithiolate (N₂S₂) or Dithiadithiolate (S₄) Platforms

Abstract

By using 3,7‐dithianonane‐1,9‐dithiol (S4) and N,N′‐dimethyl‐N,N′‐bis(2‐mercaptoethyl)ethylenediamine (N2S2) as ligands, two CH3CN‐coordinated nickel‐iron heterodimetallic complexes, [NiS4Fe(CH3CN)Cp*][PF6] (1a) and [NiN2S2Fe(CH3CN)Cp*][PF6] (1b) (Cp* = η5‐C5Me5), were synthesized and characterized spectroscopically and crystallographically. Reactivities of 1a and 1b towards CO, CH2Cl2, HBF4, and NOPF6 have also been investigated. A series of complexes coordinated with small molecules [NiS4Fe(L)Cp*][PF6]n [n = 1, L = Cl (2a), CO (3a); n = 2, L = NO (4a)], [NiN2S2Fe(L)Cp*][PF6] [L = Cl (2b), CO (3b)] were obtained. We also studied the redox properties of 2a, 2b, 3a, and 3b by cyclic voltammetry in CH2Cl2 and in CH3CN solution. Complex 3a was found to be an excellent electrocatalyst for proton reduction from HBF4.

Hemilabile Bridging Thiolates as Proton Shuttles in Bioinspired H2 Production Electrocatalysts

“…There is an extensive class of bi- and polymetallic complexes derived from transition metals, largely Ni II , in tetradentate E 2 S 2 2– (E = N, P, S) binding sites that use excess lone pairs on the cis thiolate sulfurs for binding in a bidentate manner to an additional metal, M′. , Analogous to the (η 5 -C 5 H 4 R)­Fe II (P 2 N 2 ) + complexes described above, myriad heterobimetallics have been reported in a developing area that uses η 5 -cyclopentadienide (η 5 -C 5 H 5 or η 5 -C 5 Me 5, i.e., Cp and Cp*, respectively) or η 6 -arenes bound to d 6 Fe II or Ru II , as M′, which in combination with the bridging dithiolates from the NiN 2 S 2 may offer a single open site for reactivity at M′, structure II. ,− The tunability at the π-ligand offers some control for oxidative addition in stoichiometric reactions, including both H 2 and O 2 activation. − Reports of proton reduction under electrochemical conditions by such CpFe II or CpRu II entities are scarce in the literature; however, there are examples of an S′ 2 NiS 2 (S′ = thioether sulfur; S = thiolate sulfur) metalloligand bound to CpFe′ and Cp*Fe′ that demonstrated modest electrocatalysis and H 2 production. , The MN 2 S 2 platform offers opportunity to modify a metallodithiolate ligand by changing only the M, retaining consistency in steric features such that the S-donor and M′-acceptor effects might be deconvoluted. Thus, we have designed experimental and computational protocols to analyze the proton reduction possibilities of the heterobimetallics represented in Scheme .…”

“…15,17−22 The tunability at the π-ligand offers some control for oxidative addition in stoichiometric reactions, including both H 2 and O 2 activation. 18,20 The MN 2 S 2 platform offers opportunity to modify a metallodithiolate ligand by changing only the M, retaining consistency in steric features such that the S-donor and M′-acceptor effects might be deconvoluted. Thus, we have designed experimental and computational protocols to analyze the proton reduction possibilities of the heterobimetallics represented in Scheme 2.…”

A new structural model for NiFe hydrogenases: an unsaturated analogue of a classic hydrogenase model leads to more enzyme-like Ni—Fe distance and interplanar fold

“…Several closely related models of the active site have been prepared by combining an Ni('S 4 ') fragment ('S 4 ' = dianionic tetradentate sulfur ligand) with an [FeCp R (CO)] + fragment (Cp R = Cp, C 5 H 5 or Cp*, C 5 Me 5 ), as illustrated in Fig. 1 (right) (Canaguier et al, 2010;Yang et al, 2015;Zhu et al, 2005). These complexes have an overall mono-cationic charge, consistent with formal Ni II and Fe II oxidations states.…”

“…These complexes have an overall mono-cationic charge, consistent with formal Ni II and Fe II oxidations states. The first 'S 4 ' ligand used in this capacity featured a saturated two-three-two carbon linker, in (Yang et al, 2015;Zhu et al, 2005).…”

“…In the following discussion, we compare the structural features obtained with the unsaturated ligand L 02À with those research communications of literature complexes using the saturated ligand L 2À . The structures of [Ni(L)FeCp(CO)] + , as the PF 6 À salt/ CH 2 Cl 2 solvate (Zhu et al, 2005), and [Ni(L)FeCp*(CO)] + , as the PF 6 À salt (Yang et al, 2015), are known. Both saturated analogues [Ni(L)FeCp(CO)] + and [Ni(L)FeCp*(CO)] + show Ni-Fe distances that are similar for the two, 3.1727 (6)/ 3.1529 (7) Å (two independent molecules in the unit cell) and 3.111 (5) Å , respectively, for the two complexes.…”