Cp2M

The oxidative addition reactions of Cp2M(CO)2 show some interesting differences between the Ti and Zr analogues. For Cp2Ti(CO)2, both... 

In 1987 Tapper et al. reported the first stable Mo and W complexed phosphinidenes 52 with two Cp ligands on the transition metal from the reaction of Mes PCl with Cp2M(H)Li [91]. Niecke et al. approached the syntheses of similar compounds with instead a NHMes substituent using Mes NPCl and Cp2M(H)Li... 

The migratory insertion reactions of the Ta-C functionalities in complexes 113-115 are presented in Scheme 22.9 In the reaction of 113-115 with both CO or Bu NC, the migration, under mild conditions (i.e., room temperature), of both alkyl or aryl groups to form r 2-ketones 116-118 and T 2-imino derivatives, 119-121, has been observed. Unlike the case of [Cp2M] or polyphenoxo derivatives of Ta, migration of the second alkyl or aryl group to the intermediate r 2-acyl or T 2-iminoacyl derivatives is very fast, which prevents the interception of the... 

Studies of CpLi solutions showed high conductivity, suggesting ionic particles in solution.91 Ionic particles could consist of the free ions, but anionic cyclopentadienides MCp2- particles isoelectronic to the well-known alkaline earth cyclopentadienides Cp2M (M = alkaline earth metal),103 could also be envisioned. Moreover, the structural motif of a sandwich complex where two Cp ligands bind to a metal center is well established throughout the periodic table. Indeed, the Cp2 Li anion was suggested based on NMR techniques,114-116 and... 

The use of weakly coordinating and fluorinated anions such as B(C6H4F-4)4, B(C6F5)4, and MeB(C6F5)3 further enhanced the activities of Group 4 cationic complexes for the polymerization of olefins and thereby their activity reached a level comparable to those of MAO-activated metallocene catalysts. Base-free cationic metal alkyl complexes and catalytic studies on them had mainly been concerned with cationic methyl complexes, [Cp2M-Me] +. However, their thermal instability restricts the use of such systems at technically useful temperatures. The corresponding thermally more stable benzyl complexes,... 

In the Cp2M(dithiolene) series, d° complexes were investigated essentially with Ti, and to a lesser extent with Zr and Hf, in their IV oxidation state. These complexes can be reversibly reduced to the d1, Tim anionic species but they were never isolated in the solid state. Attempts to oxidize these d° complexes were also unsuccessful, as electrochemical oxidation leads to their decomposition [23, 24]. The essential structural characteristic of these d° complexes is the strong folding of... 

Fig. 1 X-ray crystal structures of Cp2M(dithiolene) complexes (a)d° Cp2Ti(dmit) (b)d1 Cp2V (bdt) (c) d2 Cp2Mo(dmit), showing the evolution of the metallacycle folding angle...

Finally, one other example of a spin ladder has been reported within these extensive series of [Cp2M(dt)]+ salts, in the AsFfi salt of [Cp2W(dsit)]+ [34]. We will see below that the other AsFfi (Sects. 3.3.1 and 3.3.2) salts of [Cp2Mo... 

Scheme 6 Extended Htickel fragment analysis of the interaction between the partially occupied Cp2M and occupied dithiolene fragment orbitals in d1 [Cp2M(dt)]+ complexes, M = Mo, W (adapted from [69])...

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