Characterization of a Borane σ Complex of a Diiron Dithiolate: Model for an Elusive Dihydrogen Adduct.

Authors :: Lalaoui N
Woods T
Rauchfuss TB
Zampella G
Source :: Organometallics [Organometallics] 2017 Jun 12; Vol. 36 (11), pp. 2054-2057. Date of Electronic Publication: 2017 May 16.
Publication Year :: 2017
Abstract: The azadithiolate complex Fe <subscript>2</subscript> [(SCH <subscript>2</subscript> ) <subscript>26</subscript> NMe](CO) <subscript>6</subscript> reacts with borane to give an initial 1:1 adduct, which spontaneously decarbonylates to give Fe <subscript>2</subscript> [(SCH <subscript>2</subscript> ) <subscript>2</subscript> NMeBH <subscript>3</subscript> ](CO) <subscript>5</subscript> . Featuring a Fe-H-B three-center, two-electron interaction, the pentacarbonyl complex is a structural model for H <subscript>2</subscript> complexes invoked in the [FeFe]-hydrogenases. The pentacarbonyl compound is a " σ complex", where a B-H σ bond serves as a ligand for iron. The structure of this σ complex was characterized by variable-temperature NMR spectroscopy and X-ray crystallography. Complementary to the 1:1 borane adduct is the quaternary ammonium complex [Fe <subscript>2</subscript> ](SCH <subscript>2</subscript> ) <subscript>2</subscript> NMe <subscript>2</subscript> ](CO) <subscript>6</subscript> ] <superscript>+</superscript> , which was also characterized. It represents a kinetically robust analogue of the N-protonated amine cofactor, as indicated by its mild reduction potential.

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