Titanium‐Based Molecular Squares and Rectangles: Syntheses by Self‐Assembly Reactions of Titanocene Fragments and Aromatic N‐Heterocycles

Abstract

This paper reports on the potential of titanium compounds as building blocks for supramolecular polygons. Self-assembly reactions of low-valent titanocene units and N-heterocyclic bridging ligands lead to novel titanium-based supramolecular squares. Pyrazine (3), 4,4'-bipyridine (4), and tetrazine (5) were used as bridging ligands, and the acetylene complexes [Cp2Ti{eta2-C2(SiMe3)2}] (1) and [(tBuCp)2Ti{eta2-C2(SiMe3)2}] (2) as sources of titanocene fragments. Molecular rectangles can be synthesized by stepwise reduction of the titanocene dichlorides [Cp(2)TiCl2] and [(tBuCp)2TiCl2] and consecutive coordination of two different bridging ligands. The resulting complexes are the first examples of molecular rectangles containing bent metallocene corner units. Single-crystal X-ray analyses of the tetranuclear compounds revealed the geometric properties of the molecular polygons in the solid state. Comparison of bond lengths and angles in coordinated and free ligands reveals the reduced state of the bridging ligand in the low-valent titanium compounds. The syntheses and properties of these novel, highly air- and moisture-sensitive compounds are discussed.

Reactions of Titanocene- and Zirconocene-Bis(trimethylsilyl)acetylene Complexes with Selected Heterocyclic and Aromatic NH and OH Acid Compounds

“…Beckhaus and coworkers published very recently a series of excellent examples for reactions of titanocene-bis(trimethylsilyl)acetylene complexes with different N-heterocyclic compounds [11][12][13][14][15] . In these reactions the complexes Cp 2 Ti(η 2 -Me 3 SiC 2 SiMe 3 ) and Cp* 2 Ti(η 2 -Me 3 SiC 2 SiMe 3 ) act, after dissociation of the alkyne, as sources of titanocene Cp 2 Ti and permethyltitanocene Cp* 2 Ti, which dimerize and trimerize heterocycles to exciting compounds, e.g., with a cyclohexane or benzene core.…”

“…In the same manner, in the reaction of 5 with pentafluorophenol, the alkyne was eliminated and the corresponding rac-(ebthi)Zr(O-C 6 F 5 ) 2 (14) was formed (Scheme 3).…”

Reactions of Zirconocene Bis(trimethylsilyl)acetylene Complexes with Fluorinated Pyridines: C–H vs. C–F Bond Activation

“…[40][41][42][43] In these reactions, the complexes Cp 2 Ti(η 2 -Me 3 SiC 2 SiMe 3 ) and Cp* 2 Ti(η 2 -Me 3 SiC 2 SiMe 3 ) act as sources of titanocene "Cp 2 Ti" and permethyltitanocene "Cp* 2 Ti" after dissociation of the alkyne. They react differently with pyridine and fluorinated pyridines (Scheme 1 and Scheme 2).…”

A Journey from Supramolecular Chemistry to Nanoscale Networks

“…2). The N…N distances in 4,4'-bipyridine (7.134 Å) [8] and between the central tpy ring and the pendant pyridyl in 1 (7.116 Å) [9] are very similar. Complexes with nonlabile metal centres such as [Cr (1) form one-dimensional, topologically linear, polymers (Fig.…”