Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The 15 valence‐electron iron(I) complex [Cp<jats:sup>Ar</jats:sup>Fe(IiPr<jats:sub>2</jats:sub>Me<jats:sub>2</jats:sub>)] (<jats:bold>1</jats:bold>, Cp<jats:sup>Ar</jats:sup>=C<jats:sub>5</jats:sub>(C<jats:sub>6</jats:sub>H<jats:sub>4</jats:sub>‐4‐Et)<jats:sub>5</jats:sub>; IiPr<jats:sub>2</jats:sub>Me<jats:sub>2</jats:sub>=1,3‐diisopropyl‐4,5‐dimethylimidazolin‐2‐ylidene) was synthesized in high yield from the Fe<jats:sup>II</jats:sup> precursor [Cp<jats:sup>Ar</jats:sup>Fe(μ‐Br)]<jats:sub>2</jats:sub>. <jats:sup>57</jats:sup>Fe Mössbauer and EPR spectroscopic data, magnetic measurements, and ab initio ligand‐field calculations indicate an S= 3/2 ground state with a large negative zero‐field splitting. As a consequence, <jats:bold>1</jats:bold> features magnetic anisotropy with an effective spin‐reversal barrier of U<jats:sub>eff</jats:sub>=64 cm<jats:sup>−1</jats:sup>. Moreover, <jats:bold>1</jats:bold> catalyzes the dehydrogenation of N,N‐dimethylamine–borane, affording tetramethyl‐1,3‐diaza‐2,4‐diboretane under mild conditions.</jats:p>