The Lewis acidities of as eries of [n]magnesocenophanes (1a-d)h ave been investigatedc omputationally and found to be af unctiono ft he tilt of the cyclopentadienyl moieties. Their catalytic abilities in amine borane dehydrogenation/dehydrocoupling reactions have been probed, and C[1]magnesocenophane (1a)h as been shown to effectively catalyze the dehydrogenation/dehydrocoupling of dimethyl-amine borane (2a)a nd diisopropylamine borane (2b)u nder ambient conditions. Furthermore, the mechanism of the reaction with 2a has been investigated experimentally and computationally,a nd the results imply al igand-assisted mechanism involving stepwise protona nd hydride transfer, with dimethylaminoborane as the key intermediate. [a] E = bridginga tom(s) of ansa bridge;[ b] n = number of bridging atom(s) in ansa bridge.Scheme6.Reactionofm agnesium complex 5 with 2,2-dicyclopentadienylpropanetog ive magnesocenophane 1a.Scheme8.Simplified proposed catalytic cycle (coordinating solventm olecules omitted) for the dehydrogenation of Me 2 NH·BH 3 (2a)and Me 2 NHÀBH 2 ÀNMe 2 À BH 3 (3b)t oc yclic diborazane 3a,catalyzedbym agnesocenophane 1a.Scheme7.Dehydrocoupling of Me 2 NHÀBH 2 ÀNMe 2 ÀBH 3 (3b)catalyzed by 1a. Figure 10. Calculated reaction pathwaysfor the dehydrogenation of dimethylamine borane (2a)v ia dimethylaminoborane (4a), catalyzed by 1a·dme (calculated at the B3LYP-D3/def2-TZVP leveloft heory [11] ;hydrogena toms of CH 2 and CH 3 groupso mittedf or clarity).

Several new sila[2]aluminocenophane Lewis base complexes are described, which were synthesized directly from the corresponding sila[2]magnesocenophane and AlX·base precursors. The compounds are stable at room temperature for weeks, and were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single crystal X-ray diffraction. In all cases, a dynamic structure was observed in solution, due to rapid sigmatropic rearrangements. Bonding energies of the Lewis base ligands to the aluminium center were calculated to be 162.9-213.3 kJ mol.

A bis(aluminocenophane) with a remarkably short Al–Al single bond, which was studied in detail by DFT calculations, is presented.

The synthesis and characterization of polyferrocenylmethylene (PFM) starting from dilithium 2,2‐bis(cyclopentadienide)propane and a Me2C[1]magnesocenophane is reported. Molecular weights of up to Mw = 11 700 g mol–1 featuring a dispersity, Ð, of 1.40 can be achieved. The material is studied by different methods comprising nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization time of flight (MALDI‐ToF) mass spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements elucidating the molecular structure and thermal properties of these novel polymers. Moreover, cyclic voltammetry (CV) reveals quasi‐reversible oxidation and reduction behavior and communication between the iron centers. Also, the crystal structure of a related cyclic hexamer is presented.

Several new diphenylamino-and diphenylphosphanyldialkylalanes are reported, which were characterized in solution and in the solid state, assisted by in-depth bonding analysis within the DFT framework. In the case of bulky alkyl substituents on the aluminum atom, the species are stable in their monomeric form and were structurally characterized by single crystal X-ray diffraction, expanding the relatively small field of monomeric pnictogenylalanes. In the case of oligomeric diphenylpnictogenyldimethylalanes, their reactivity toward different σ-donor ligands was studied, and several examples of monomeric adducts could be structurally characterized, including the first cyclic(alkyl)(amino)carbene complexes. The reactivity of these CAAC complexes, their oligomeric precursors, and an unstabilized monomeric aminoalane toward CO 2 was probed, leading to different insertion products that could be characterized. Additionally, the mechanism was elucidated by DFT calculations.

The Cover Feature shows a donor‐stabilized monocarba‐bridged bis(cyclopentadienyl)alane. Several examples of these compounds were synthesized, and characterized in solution and in the solid state. They are structurally related to metallocenophanes, but were found to possess a butterfly‐type structure in the solid state with η1 bonded cyclopentadienyl groups. More information can be found in the Full Paper by Wasim Heider et al.

A C[1]magnesocenophane catalyzes the dehydrocoupling reaction of dimethylamine borane to the cyclic tetramethyldiborazane under ambient conditions. While there are many transition‐metal‐based catalysts known to facilitate this reaction at room temperature, it is quite remarkable for a magnesium compound, as previous magnesium‐based systems required elevated temperatures. The mechanism has been investigated by experimental and theoretical means and a ligand‐assisted route is proposed. More information can be found in the Full Paper by A. Schäfer et al. on page 6176.

Five monocarba‐bridged bis(cyclopentadienyl)aluminum halide NHC and thione complexes and one monocarba‐bridged bis(cyclopentadienyl)phosphanylalane NHC complex are reported. The former were synthesized by transmetalation of a C[1]magnesocenophane with the corresponding aluminum(III) chloride and aluminum(III) bromide donor adducts. The phosphanylalane complex was obtained by a subsequent functionalization of the corresponding bromoalane with lithium diphenylphosphide. All complexes were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single crystal X‐ray diffraction. Bonding energies of the NHC and thione ligands to the aluminum centres were estimated by DFT calculations.