Insight in Structures of Superbulky Metallocenes with the CpBIG Ligand: Theoretical Considerations of Decaphenyl Metallocenes

(η4-Tetraphenylcyclobutadiene)-(η5-pentaphenylcyclopentadienyl)-cobalt

A one-pot reaction starting with C5Ph5Br, n-BuLi and [CoCl(PPh3)3] followed by the addition of diphenylethyne produces the title compound with 12% yield. Spectroscopic characterization involved 1H, 13C-NMR, UV-Vis and mass spectrometry. A crystal structure determination showed that the central aromatic rings are exactly parallel with the cyclobutadiene ring further apart from the metal as usual. The pentaphenyl–cyclopentadienyl ligand shows an usual paddlewheel orientation, whereas in the tetraphenyl–cyclobutadiene ligand, two of the phenyl groups are nearly coplanar with the four-membered ring. There are also numerous C–H…C(π) interactions between the phenyl groups on the same ring, as well as between rings.

Bulking up CpBIG: A Penta-Terphenyl Cyclopentadienyl Ligand

The modification of cyclopentadienyl ligands with carefully selected substituents is a widely used strategy for tuning their steric and electronic properties. We describe the synthesis of an extremely bulky penta-terphenyl cyclopentadienyl ligand (Cp^T5) by arylation of cyclopentadiene. Deprotonation reactions with various group 1 metals and bases afforded a complete series of alkali metal salts MCp^T5 (M = Li–Cs). The compounds were isolated as solvate-free salts, which were characterized by multinuclear nuclear magnetic resonance spectroscopy, ultraviolet–visible spectroscopy, and elemental analysis. Single-crystal X-ray diffraction studies of LiCp^T5, NaCp^T5 (crystallized as a solvate with one tetrahydrofuran molecule per formula unit), and KCp^T5 revealed the formation of metallocene-like sandwich structures in the solid state.

Half-sandwich scandium dibenzyl complexes bearing penta- or tetra-arylcyclopentadienyl ligands: synthesis, structure and syndiospecific styrene polymerization activity

A series of half-sandwich scandium dibenzyl complexes has been synthesized via a reaction of KCp^(Ar*)5 or KCp^Ar5 (Ar* = 3,5-^tBu₂–C₆H₃; Ar = 3,5-ⁱPr₂–C₆H₃) or KCp^(Ar*)4H, KCp^Ar4H and KCp^Ph4H with the cationic scandium complex [Sc(p-CH₂C₆H₄-Me)₂(THF)_x][BPh₄].