A New C2-Symmetric Ligand for ansa-Metallocene Chemistry: Synthesis and X-ray Crystal Structure of the ansa-Stannocene Complex rac-[(CHBut)2(C5H2But2)2]Sn

Main-Group Metallocenophanes

Metallocenes with interlinked cyclopentadienide ligands are commonly referred to as ansa-metallocenes or metallocenophanes. These can have drastically different properties than their unbridged parent compounds. While this concept is best known for transition metals such as iron, it can also be adopted for many main-group elements. This review aims to summarize recent advances in the field of metallocenophanes based on main-group elements of group 2, group 13, group 14 and group 15, focusing on synthesis, structure and properties of these compounds.

Synthesis, Structure, and Reactivity of Disiloxa[3]tetrelocenophanes

Tetramethyldisiloxa[3]metallocenophanes of the heavy group 14 elements germanium, 2a, tin, 2b, and lead, 2c, (tetrelocenophanes) have been synthesized by the reaction of dilithiated ligand, 1, with the corresponding element(II) chloride. The plumbocenophane, 2c, forms one-dimensional coordination polymers in the solid state, while the germanocenophane, 2a, and the stannocenophane, 2b, are monomeric. Furthermore, the reactivity of the stannocenophane, 2b, and the plumbocenophane, 2c, toward N-heterocyclic carbenes was explored. Although the coordination of carbene is reversible in solution at room temperature, the corresponding carbene complexes, 3a,b, could be structurally characterized, illustrating the Lewis acidity of the central atom in these metallocenophanes.

Permethylated Disila[2]metallocenophanes of Group 14 and 15 Elements

Permethylated disila[2]metallocenophanes of silicon, germanium, tin, lead, 2 a-d, (tetrelocenophanes) and antimony, 3 a,b, (pnictogenocenophanes) are described. In the case of antimony, a chloro-substituted stibonocenophane, 3 a, as well as cationic stibonocenophanium tetrachloroaluminate and tetraphenylborate salts, 3 b[X] (X=[AlCl₄ ], [BPh₄ ]), were synthesized. These represent the first examples of metallocenophanes of any Group 15 element. All compounds were studied in solution and in the solid state. Without exception the ansa-bridge exerts a strong influence on the bending angle of the two Cp-ligands. For disila[2]plumbocenophane, 2 d, its reactivity towards Group 15 halides was probed. Treatment of disila[2]plumbocenophane, 2 d, with two equivalents of phosphorus(III) chloride or arsenic(III) chloride, results in a ring-opening reaction and gives the bis(dihalopnictogenyl)-substituted products, 4 a,b.

A bis(aluminocenophane) with a short aluminum–aluminum single bond

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

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 by transmetalation.