A lithium-aluminium heterobimetallic dimetallocene.

Homobimetallic dimetallocenes exhibiting two identical metal atoms sandwiched between two η5 bonded cyclopentadienyl rings is a narrow class of compounds, with representative examples being dizincocene and diberyllocene. Here we report the synthesis and structural characterization of a heterobimetallic dimetallocene, accessible through heterocoupling of lithium and aluminylene fragments with pentaisopropylcyclopentadienyl ligands. The Al-Li bond features a high ionic character and profits from attractive dispersion interactions between the isopropyl groups of the cyclopentadienyl ligands. A key synthetic step is the isolation of a cyclopentadienylaluminylene monomer, which also enables the structural characterization of this species. In addition to their structural authentication by single-crystal X-ray diffraction analysis, both compounds were characterized by multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, reactivity studies of the lithium-aluminium heterobimetallic dimetallocene with an N-heterocyclic carbene and different heteroallenes were performed and show that the Al-Li bond is easily cleaved.

Bis(tetrelocenes) - fusing tetrelocenes into close proximity.

We report the synthesis and structure of two bis(germanocenes) and a bis(stannocene), obtained by the reaction of unsymmetric ansa bis(cyclopentadienyl) ligands with germanium and tin dichloride. DFT calculations show that the formation of these bis(tetrelocenes) is energetically favoured over the formation of the corresponding [1]tetrelocenophanes. In the crystal structure authenticated structural motif, the two tetrel(II) centers are forced into close proximity to each other, resulting in weak donor-acceptor interactions, according to Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) analyses.

Heavier N-heterocyclic half-sandwich tetrylenes.

ansa-Half-sandwich complexes of the group 14 elements germanium, tin and lead are reported, which represent a new class of Lewis amphiphilic tetrylenes and bridge the gap between classical N-heterocyclic systems and group 14 metallocenes. These compounds can form complexes both with carbenes and transition metal fragments.

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.

Diphosphanylmetallocenes of Main-Group Elements.

Several 1,1'-diphosphanyl-substituted metallocenes of magnesium (magnesocenes) were synthesized, structurally characterized, and their reactivity and coordination chemistry were investigated. Transmetalation of these magnesocenes gives access to group 14 metallocenes (tetrelocenes), as well as to group 15 stibonocenes. These s- and p-block metallocenes represent a novel class of bis(phosphanyl) ligands, exhibiting Lewis-amphiphilic character. Their coordination chemistry towards different transition-metal and main-group fragments was investigated and different complexes are presented.

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.