Complexes with Metallocene Ligands

Since the first report in 1987 by Green et al. [4], metallocene derivatives represent one of the most widely investigated classes of second-order NLO metal-based chromophores [114-116]. Starting from the prototypical stilbene (trani)-l-ferroce- 

Some related ruthenocene species have also been investigated [117], almost always showing lower quadratic hyperpolarizabihties, in accordance with the higher ionization energy of the ruthenocene vs ferrocene moiety [115]. 

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Edelmann FT (1996) Rare Earth Complexes with Heteroallylic Ligands. 179 113-148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Ekhart CW, see de Raadt A (1997) 187 157-186... 

Edelmann FT (1996) Rare Earth Complexes with Heteroallylic Ligands. 179 113 -148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Effenhauser CS (1998) Integrated Chip-Based Microcolumn Separation Systems. 194 51 - 82 Ehrfeld W, Hessel V, Lehr H (1998) Microreactors for Chemical Synthesis and Biotechnology -Current Developments and Future Applications. 194 233 - 252 Ekhart CW, see de Raadt A (1997) 187 157-186... 

It is noteworthy that the benzamidinate ligands lie in two nonsymmetrical planes. Comparing the benzamidinate ligation in these complexes with metallocenes, using the benzamidinate central carbon as the centroid, shows that between two Zr atoms the cone angle is 124.8(3)°, whereas in metallocenes this angle is 136°. 

The chemistry of organolanthanides has been dominated by complexes with metallocene and half-sandwich ligand systems because of the rigidity, steric bulk, thermal and chemical stability of the cyclopentadienyl ligands. However, driven by the desire to explore novel structural... 

In this review, no ansa metallocene complexes with indenyl ligands are incorporated due to the already existing comprehensive literature. Furthermore, it would have been necessary to repeat all polymerization experiments with these complexes in order to obtain results for a comparison with the already established parameters. 

CyDs form crystalline complexes with metallocenes. Crystallographic study of several metallocene complexes of a-CyD and -CyD has been reported [226-228]. These complexes mostly crystallize in a head-to-head channel-type packing structure. In the a-CyD complex with ferrocene, the metal ion is located at the center of the dimer cavity and the host a-CyD molecule has direct contacts only with the cyclopentadienyl ligands [226]. Some metallocenium complexes of a-CyD exhibit a similar structure [227, 228]. Anions such as PFfi are bound at the primary hydroxyl side (Fig. 7.24). 

Complexes with Dianionic Ligands. In the search for metallocenes that do not require ionization, several workers have targeted the synthesis of Group IV complexes in which a dianionic ligand replaces a monoanionic Cp of bis-Cp metallocenes. Bazan has found good activity for TMM 23 (trimethylenemethane dianion) and TBM 24, (tribenzylidenemethane dianion) complexes of zirconium (89). 

Abstract The development of a sa-metallocene catalysts is considered along several lines of interest - ansa-metallocene complexes with different ligand frameworks, insights gained with regard to relevant reaction intermediates and contributions of ansa-metallocene catalysts to industrial polymer production -with a view toward the present state of the art in these fields of catalysis research. 

Cp acting as a or rj -ligand are relatively rare. Structure 2.45 is an example of a high-valent Cp complex with oxo ligands. Because of the presence of oxo ligands, they have been studied as potential oxidation catalysts. Structure 2.46 is an example of a rare Zn metallocene with a metal-metal bond. Its structure, hke that of many other Cp complexes, can be explained by simple electron counting schemes (see Section 2.3.2). 

Therefore, this chapter focuses on the C-C bond cleavage using metallocenes or metal complexes with cyclopentadienyl ligands or related ligands. 

More recently, a very efficient asymmetric carbolithiation of N,N-dimethyl-aminofulvene 30, leading to a chiral cyclopentadienide anion, was reported by Hayashi et al. [6] for the synthesis of chiral metallocenes (Scheme 6). By adding an aryl lithium such as 31 complexed with a chiral ligand on fulvene 30, a cyclopentadienide ion 32 bearing a stereogenic center at the a position was generated. This anion was reacted with [RhCl(nbd)]2 to yield... 

Metallocenes with substituted cyclopentadienyl rings. Metallocenes with methylated rings were among the first heavy alkaline earth metallocenes to be structurally characterized, but many other substituents have been incorporated into bis(cyclopentadienyl) complexes. Under this classification are included compounds with indenyl ligands, which in... 

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