The amino imidazolin-2-imine ligand [HAmIm, 1,2-(DippNH)–C6H4–NC(NiPrCMe)2] is employed in the synthesis of the paramagnetic cobalt(I) arene complex Co(AmIm)(η 6 -C6H6). The latter was found to be a highly efficient (pre)catalyst in H/D exchange reactions with deuterium (D2) in hydrosilanes. The scope comprises primary to tertiary silanes at a low catalyst loading of 1 mol %. Additionally, the same cobalt(I) arene complex was able to catalyze hydrosilylation reactions of terminal olefins with primary to tertiary silanes at low catalyst loadings of 0.5 mol %. The scope of hydrosilylation includes intramolecular hydrosilylation to produce silacarbocycles and multiple hydrosilylation with primary silanes. The mechanistic investigation includes numerous control experiments for both H/D exchange and hydrosilylation. Isolated (trapped) cobalt(III) hydride silyl complexes (including X-ray crystallographic authentication) are presented for primary to tertiary Si–H entities, which demonstrates a wide scope of Si–H bond activation by the low-valent Co(AmIm) core. The experimental results are strongly corroborated by density functional theory calculations, which explore the possible reaction mechanisms of studied reactions.

We present facile access to an alumaborane species with electron precise AlÀ B σ-bond. The reductive rearrangement of 1-(AlI 2 ), 8-(BMes 2 ) naphthalene (Mes = 2,4,6-Me 3 C 6 H 2 ) affords the alumaborane species cyclo-(1,8-C 10 H 6 )-[1-Al(Mes)(OEt 2 )-8-B(Mes)] with a covalent AlÀ B σ-bond. The AlÀ B σ-bond performs the reductive scission of multiple bonds: S=C(NiPrCMe) 2 affords the naphthalene bridged motif BÀ SÀ Al(NHC), NHC = N-heterocyclic carbene, while O=CPh 2 is deoxygenated to afford an BÀ OÀ Al bridged species with incorporation of the remaining �CPh 2 fragment into the naphthalene scaffold. The reaction with isonitrile Xyl-N�C (Xyl = 2,6-Me 2 C 6 H 4 ) proceeds via a proposed (amino boryl) carbene species; which adds a second equivalent of isonitrile to ultimately form the AlÀ NÀ B bridged species cyclo-(1,8-C 10 H 6 )-[1-Al(Mes)-N(Xyl)-8-B{C(Mes)=CÀ NÀ Xyl}] with complete scission of the C�N triple bond. The latter reaction is supported with isolated intermediates and by DFT calculations.

Es wird ein einfacher Zugang zu einer Alumaboran-Spezies mit elektronenpräziser AlÀ B σ-Bindung vor-gestellt. Die reduktive Umlagerung von 1-(AlI 2 ), 8-(BMes 2 )-Naphthalin (Mes = 2,4,6-Me 3 C 6 H 2 ) ermöglicht die Bildung der Alumaboran-spezies cyclo-(1,8-C 10 H 6 )-[1-Al(Mes)(OEt 2 )-8-B(Mes)] mit einer ko-valenten AlÀ B σ-Bindung. Diese AlÀ B σ-Bindung bewirkt die reduktive Spaltung von Mehrfachbindungen: S=C-(NiPrCMe) 2 ergibt die naphthalinverbrückende Struktur BÀ SÀ Al(NHC), NHC = N-Hetero-cyclisches Carben, während O=CPh 2 desoxygeniert wird, um eine BÀ OÀ Alverbrückende Spezies zu erhalten, bei der das verbliebene = CPh 2 -Fragment in das Naphthalingerüst eingebaut wird. Die Re-aktion mit Isonitril Xyl-N�C (Xyl = 2,6-Me 2 C 6 H 4 ) erfolgt über eine vorgeschlagene (Aminoboryl-)Carben-Spezies, die ein weiteres Äquivalent Isonitril hinzufügt, um die AlÀ NÀ B-verbrückende Spezies cyclo-(1,8-C 10 H 6 )-[1-Al(Mes)-N(Xyl)-8-B{C(Mes) = CÀ N-Xyl}] unter voll-ständiger Spaltung der C�N-Dreifachbindung zu bilden. Die letztgenannte Reaktion wird anhand isolierter Zwischenstufen sowie durch DFT-Berechnungen unterstützt.

Donor‐acceptor cyclopropanes or cyclobutanes are dipolar reagents, which are widely used in the synthesis of complex organic (hetero)cycles in ring expansion reactions. Applying this concept to boron containing heterocycles, the four‐membered borete cyclo‐iPr2N‐BC10H6 reacted with the carbon donor ligands 2,6‐xylylisonitrile and the carbene IMes :C(NMesCH)2 with ring expansion and ring fusion, respectively. In particular, the tetracyclic structure formed with IMes displays zwitterionic character and absorption in the visible region. In contrast to the carbene IMes, the heavier carbenoids :Si(NDippCH)2 and :Ga(AmIm) with a two‐coordinate donor atom afford spiro‐type bicyclic compounds, which display four‐coordinate geometry at silicon or gallium. (TD‐)DFT calculations provide deeper insight into the mechanism of formation and the absorption properties of these new compounds.

Among other main group elements, the chemistry of boron has been stimulated by N-heterocyclic carbenes (NHCs) as important ligands, the nature of which can significantly control the outcome of reactions. In four-coordinate benzyl boranes of type (NHC)BH 2 CH 2 (o-BrC 6 H 4 ), we demonstrate this effect at the example of a lithiation silylation procedure. For NHC = IiPr lithiation of the arene ring by lithium-bromide exchange with tBuLi ultimately leads to backbone substitution with proton rearrangement, as demonstrated by trapping with trimethylsilyl chloride. In contrast, such process is suppressed for NHC = IiPr Me , which undergoes lithiation and subsequent trimethyl-silylation at the arene moiety.