Characterizing the Biosynthesis of the [Fe(II)(CN)(CO)(cysteinate)] Organometallic Product of the Radical-SAM Enzyme HydG by EPR and Mössbauer Spectroscopy.

[FeFe]-hydrogenases employ a catalytic H-cluster, consisting of a [4Fe-4S] cluster linked to a [2Fe] subcluster with CO, CN ligands, and an azadithiolate bridge, which mediates the rapid redox interconversion of H and H. In the biosynthesis of this H-cluster active site, the radical -adenosyl-l-methionine (radical SAM, RS) enzyme HydG plays the crucial role of generating an organometallic [Fe(II)(CN)(CO)(cysteinate)] product that is en route to forming the H-cluster. Here, we report direct observation of this diamagnetic organometallic Fe(II) complex through Mössbauer spectroscopy, revealing an isomer shift of δ = 0.

Lewis acid capping of a uranium(v) nitride via a uranium(iii) azide molecular square.

Reaction of (CpiPr4)2UI with NaN3 resulted in formation of tetrameric uranium(iii) azide-bridged 'molecular square' [(CpiPr4)2U(μ-η1:η1-N3)]4 (1). Addition of B(C6F5)3 to 1 induced loss of N2 at room temperature, yielding the uranium(v) borane-capped nitrido (CpiPr4)2U(μ-N)B(C6F5)3 (2).