Synthesis and Electrocatalytic Property of Diiron Hydride Complexes Derived from a Thiolate-Bridged Diiron Complex

Interaction of a diiron thiolate-bridged
complex, [Cp*Fe­(μ-η2:η4-bdt)­FeCp*] (1) (Cp* = η5-C5Me5; bdt = benzene-1,2-dithiolate) with a proton
gives an FeIIIFeIII hydride bridged complex,
[Cp*Fe­(μ-bdt)­(μ-H)­FeCp*]­[BF4] (3­[BF4]). According to in situ variable temperature 1H NMR studies,
the formation of 3­[BF4] was evidenced to occur through a stepwise pathway: protonation occurring
at an iron center to produce terminal hydride [Cp*Fe­(μ-bdt)­(t-H)­FeCp*]­[BF4] (2) and subsequent
intramolecular isomerization to bridging hydride 3­[BF4]. A one-electron reduction
of 3­[BF4] by CoCp2 affords a paramagnetic mixed-valent FeIIFeIII hydride complex, [Cp*Fe­(μ-η2:η2-bdt)­(μ-H)­FeCp*] (4).
Further, studies on protonation processes of diruthenium and iron–ruthenium
analogues of 1, [Cp*M1­(μ-bdt)­M2Cp*]
(M1 = M2 = Ru, 5; M1 = Fe, M2 = Ru, 8),
provide experimental evidence for terminal hydride species at these
bdt systems. Importantly, diiron or diruthenium hydride bridged complexes 3­[BF4], 7­[BF4] and iron–ruthenium
heterodinuclear complex 8­[PF6] can realize electrocatalytic hydrogen evolution.