Ein neuartiger Zugang zu Fulvenkomplexen des Titans - diastereoselektive Komplexierung von Pentafulvenen an Cyclopentadienyltitan-Fragmente

Abstract

Konkurrenz bekommen die bekannten thermisch induzierten Synthesen von Fulvenkomplexen früher Übergangsmetalle mit der direkten reduktiven Anbindung von Pentafulvenen an CpTiCl‐Fragmente. Diese meist hoch diastereoselektiven Reaktionen (siehe Schema) ermöglichen eine breite Variation der Substitutionsmuster und eröffnen eine umfangreiche Folgechemie.

Theoretical studies on titanium pentafulvene complexes

“…Preparation of 1: a solution of 1.764 g (5 mmol) of 3 [46] in 20 mL Et 2 O is added to 3.28 ml (5.25 mmol) MeLi (1.6 M in Et 2 O) at À78°C. The mixture is warmed up under stirring to room temperature and stirred for 1 h at 25°C.…”

“…All of the complexes 1-6 show a distinct color, and their UV-Vis spectra have been recorded [46,47,56]. It therefore seems straightforward to theoretically investigate the excitation behavior which allows the correct reproduction of excitation energies and gives information on the nature of the excitation.…”

“…In such a way, the monocyclopentadienyltitaniumpentafulvene chlorides (2)(3)(4)(5) [46][47][48] as well as derivatives there of (e.g., 1) becomes available in acceptable yields (Table 1, Fig. 1).…”

“…Experimental studies with titanium complexes 1-6, including UV-Vis and NMR investigations as well as crystallographic data, indicate that these complexes exist in a coordination between the dianionic (E) and an olefinic form (D) [46][47][48]56]. We therefore set out to theoretically analyze this situation using geometry optimizations, excited states calculations and population analyses.…”

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

“…Aditionally, by other reactions the conversion of only one pentafulvene [C 5 H 4 =CR 2 ] 2− to Cp′ ligands [C 5 H 4 −CHR 2 ] 1− was described whereas the other remains as [C 5 H 4 =CR 2 ] 2− ligand. This opens the way to a lot of other synthetically very interesting reactions …”