Beyond S and Se: Electrocatalytic Hydrogen Production by Tellurolate-Bridged Co(III)-Mn(I) Heterodinuclear Complexes.

In the pursuit of efficient electrocatalysts for the hydrogen evolution reaction (HER), a series of manganese and cobalt heterodinuclear complexes have been synthesized and characterized that have a stark resemblance with the [NiFe]-hydrogenase active site structure. Irradiation of [Mn ₂ (CO) ₁₀ ] in the presence of 1.5 eq of [NaEPh] [E = S, Se, Te] followed by reaction with [Cp*CoCl] ₂ led to the formation of half-sandwiched trichalcogenate-bridged heterodinuclear complexes [{Mn(CO) ₃ }(μ-EPh) ₃ (CoCp*)] [E = S ( C1 ); Se ( C2 ) and Te ( C3 )]. The reaction of these heterodinuclear trichalcogenate-bridged complexes with [LiBH ₄ ·THF] yielded the corresponding dichalcogenate hydride-bridged heterobimetallic complexes [(CO) ₃ Mn(μ-EPh) ₂ (μ-H)(CoCp*)] [E = S ( C5 ); Se ( C6 ) and Te ( C7 )], which closely imitate the Ni-R intermediate of [NiFe]-hydrogenase. The resultant complexes ( C5-C7 ) displayed impressive H ₂ production in DMF in the presence of HBF ₄ , whereas the Te-based complex ( C7 ) showcased the highest TON (184 h ^-1 ) with an impressive Faradaic efficiency of >98%. The DFT investigations revealed a unique role of bridging chalcogens in catalysis, wherein, depending on the identity of the chalcogen (S, Se, or Te), protonation could occur via two distinct routes. This study represents a rare example of the full trio of S/Se/Te-based heterodinuclear complexes whose electrocatalytic HER activity has been probed under analogous conditions.