Inhibition of [FeFe]-hydrogenase by formaldehyde: proposed mechanism and reactivity of FeFe alkyl complexes

Abstract

The mechanism for inhibition of [FeFe]-hydrogenases by formaldehyde is examined with model complexes.

Hybrids of [FeFe]- and [NiFe]-H2ase Active Site Models

“…The Fe1–C2 and Ni1–C2 distances are 1.839(10) and 2.908(10) Å, respectively. Structurally, [ 4 ] + is related to the diiron complex [(CO) 2 (PMe 3 )­Fe­[(μ-SCH 2 ) 2 NCH 2 ]­Fe­(CO) 2 (PMe 3 )] + , which also has an Fe­( C H 2 )­(CO) 3 S 2 center . The 13 C NMR spectrum of [ 4 ]­BAr F 4 displays only two C O resonances, consistent with its symmetry.…”

“…No reaction was observed between [ 4 ] + and PPh 3 . In contrast, [Fe 2 [(μ-SCH 2 ) 2 NCH 2 ]­(CO) 4 (PMe 3 ) 2 ] + alkylates PPh 3 , giving the phosphonium derivative [Fe 2 [(μ-SCH 2 ) 2 NCH 2 PPh 3 ]­(CO) 4 (PMe 3 ) 2 ] + …”

“…This reactivity highlights the lability of the adt cofactor in models. 36,40 The involvement of a formaldehyde or its equivalent in the degradation is supported by experiments using 13 CH 2 O. As supported by the stability of [(dppv)Ni(μadt)(μ-H)Fe(CO) 2 (PPh 3 )] + and Fe 2 (μ-adt)(CO) 4 (PMe 3 ) 4 , the adt ligand is robust in electron-rich dimetallic centers, a fact that may be relevant to the resilience of the [FeFe] H center in the enzyme.…”

Synthesis, Characterization and Electrochemical Studies of bis(Monothiolato) {FeFe} Complexes [Fe2(μ‐SC6H4‐OMe‐m)2(CO)5L] (L = CO, PCy3, PPh3)

“…Furthermore, most of the studies have considered mainly dithiolates as the linkers [1,19–50] . Only recently, the focus has shifted to monothiolate‐based {FeFe} systems.…”

Hydride state accumulation in native [FeFe]-hydrogenase with the physiological reductant H2 supports its catalytic relevance

“…46,47 In the latter case, binding of formaldehyde on the [2Fe] subsite via a Fe-C bond was proposed from a combination of ENDOR spectroscopy and DFT calculations, 48 and further supported by studies of model complexes. 49 Whether a similar binding model can be applied also to carboxylic acids remains to be verified. The extent of the new state (H ox c) formed in electrochemistry setups, its role in catalysis and its implication on catalytic currents, especially at low pH, remain unclear.…”