endoandexoIsomers of Isodicyclopentadienyltrichlorotitanium

Abstract

The diastereomeric endo and exo isomers of the title complex, [TiCl3(C10H11)], have been synthesized by electrophilic attack of TiCl4 on the exo- or endo-trimethylsilyl derivative of isodiCp (isodiCp = isodicyclopentadiene). This reaction proceeds with net inversion of configuration to give exclusively either the endo- or exo-(isodiCp)TiCl3 compound. Although the two isomers have similar unit-cell constants, they crystallize in different space groups. The endo complex, (2), is in Pbcm with a crystallographic mirror plane, while the exo complex, (4), is in Pca2(1) with pseudo-mirror symmetry. Both molecules display a distorted tetrahedral geometry about the Ti atom. Each Ti atom is bonded in a eta(5) manner to the Cp ring of the isodiCp ligand, with Ti--ring centroid distances of 2.031 (2) and 2.013 (2) A for (2) and (4), respectively. A slight bending of the isodiCp ligand about the bond shared by the Cp ring and the norbornane fragment is observed in both structures. The determination of the absolute structure of (4) defines the directionality of the packing along the polar c axis.

Stereoselective Access to New Half-Sandwich Complexes Containing an Isodicyclopentadienyl Ligand

“…Isodicyclopentadienide anion 1 was obtained by conventional reaction of isodicyclopentadiene with n -butyllithium in ether at −78 °C. ,, Reaction of 1 at −78 °C with a large excess of dichlorodimethylsilane in THF led to chloro(dimethyl)(isodicyclopentadienyl)silane ( 2 ) in 81% yield. In related published works, − the influence of reaction temperature on stereoselectivity was demonstrated. At −78 °C, the endo product is obtained nearly exclusively.…”

Li+ cation coordination by acetonitrile—insights from crystallography

“…The ether O-Li + cation coordination bond lengths for (12C4) 2 :LiX solvates, however, are quite long (typically 2.21-2.54 A ˚with an average of approximately 2.37 A ˚from reported crystal structures), indicating relatively weak coordination bonds due to the small size of the Li + cations and difficulty of packing eight donor atoms about the cation. [15][16][17][18] In contrast, monoglyme (G1) and diglyme (G2) are able to form (G1) 3 :LiX and (G2) 2 :LiX solvates with six-fold coordination (Fig. 1) and shorter ether O-Li + cation coordination bonds (typically 2.05-2.24 and 2.00-2.27 A ẘith averages of approximately 2.13 and 2.13 A ˚, respectively, from reported crystal structures).…”

Solid-State Structural Analysis of the “Naked” Isodicyclopentadienide Anion

“…The question of the actual structure of 3 has more recently been probed by X-ray diffraction methods. Initially, the lithium aggregation isomers 4 and 5 were secured in crystalline form from the equilibrating system in a selective manner …”