Diarylpnictogenyldialkylalanes─Synthesis, Structures, Bonding Analysis, and CO2 Capture.

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 CO2 was probed, leading to different insertion products that could be characterized. Additionally, the mechanism was elucidated by DFT calculations.

Rings and Chains: Synthesis and Characterization of Polyferrocenylmethylene.

The synthesis and characterization of polyferrocenylmethylene (PFM) starting from dilithium 2,2-bis(cyclopentadienide)propane and a Me2 C[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.

Donor-Stabilized Monocarba-Bridged Bis(cyclopentadienyl)alanes.

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.

Magnesocenophane-Catalyzed Amine Borane Dehydrocoupling.

The Lewis acidities of a series of [n]magnesocenophanes (1 a-d) have been investigated computationally and found to be a function of the tilt of the cyclopentadienyl moieties. Their catalytic abilities in amine borane dehydrogenation/dehydrocoupling reactions have been probed, and C[1]magnesocenophane (1 a) has been shown to effectively catalyze the dehydrogenation/dehydrocoupling of dimethylamine borane (2 a) and diisopropylamine borane (2 b) under ambient conditions. Furthermore, the mechanism of the reaction with 2 a has been investigated experimentally and computationally, and the results imply a ligand-assisted mechanism involving stepwise proton and hydride transfer, with dimethylaminoborane as the key intermediate.

A bis(aluminocenophane) with a short aluminum-aluminum single bond.

A bis(dicarba[2]aluminocenophane) was synthesized by reduction of a corresponding dichloro precursor with 1,3-ß-diketiminate magnesium(i). The bis(aluminocenophane) is stable under an inert gas atmosphere and was characterized in solution and in the solid state. The crystal structure reveals an unusually short Al-Al single bond and two η5 coordinated cyclopentadienyl groups on each aluminum atom which are disposed in an orthogonal fashion. The aluminum bond can be oxidized and cleaved by element chlorides and tert-butyl isonitrile. The bonding situation was studied within the DFT framework.

Lewis base complexes of sila[2]aluminocenophanes.

Several new sila[2]aluminocenophane Lewis base complexes are described, which were synthesized directly from the corresponding sila[2]magnesocenophane and AlX3·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-1.