Dicyclopentadienyl complexes

Bridges containing SiOSi units have been introduced by condensation reactions of dicyclopentadienyl complexes containing functionalized silyl groups (equation 53)84-107 or by oxygen insertion into a preformed Si-Si bridge (equation 54)108. 

Two classes of material will be described here - the metal dithiolenes and rare earth metallocenes. In the metal dithiolenes a strong, low energy pi-pi transistion occurs in the near IR (9.10). This can be tuned from about 700 nm to 1400 nm by altering the metal ion, substituents or charge state of the dithiolene. The dithiolenes are particularly attractive because of their optical stability which has been exploited in their use as laser Q-switch materials. In the rare earth complexes the near IR band is provided by/-/transistions of the rare earth ion rather than the cyclopentadienyl ring structure various nonlinear optical phenomena have been observed in glasses incorporating similar ions. Previous studies have shown that dicyclopentadienyl complexes such as ferrocene have off-resonant nonlinearities similar to nitrobenzene or carbon disulphide (11-13)... 

The mass spectra of the dicyclopentadienyl complexes, MCp2 (M = V, Cr, Fe, Ni, Co, Ru, Mn, or Mg), and the hydride Cp2ReH, show little evidence of loss of anything other than Cp groups or metal atoms in the... 

The dimethylsilyl-bridged dicyclopentadienyl complex [Me2Si(3-Me3SiC5 H3)2]NdCl (Scheme 10) was successfully applied for the preparation of a strongly alternating BD/ethylene-copolymer (Sect. 2.3.5) [306]. 

Figure 9.9. Skeletal vibrations of metal dicyclopentadienyl complexes.

Unlike dicyclopentadienyl complexes of divalent REM, the complexes of trivalent lanthanoids react very slowly with carbon dioxide under mild conditions. After standing 3 hours in saturated with CO2THF the IR spectrum of Cp3Pr practically does not change [56]. 

There are two types of compounds of this class dicyclopentadienyl complexes Cp2-LnX and monocyclopentadienyl derivatives CpLnX2- Each electronegative atom or group can be in the role of substituent X. Properties of these complexes are shown in the corresponding sections of this Chapter (Tables HI. 12 and HI. 14). Amides, phosphides, alkoxides, thiolates, selenolates and organometallic REM derivatives of Cp2LnXR type, belonging to the same class of compounds, are considered in Chapters V-X. 

Many 7i-cyclopentadienyl complexes may be prepared from the reaction of alkali metal cyclopentadienides with ammonia-soluble transition metal salts such as nitrates and thiocyanates in liquid ammonia (2-30). The amine complexes, [M(NH3) ] (C5H5)2, lose ammonia when heated in vacuo, and the uncharged dicyclopentadienyl complexes of iron, cobalt, nickel, chromium, and manganese are obtained. 

Also useful for dicyclopentadienyl complexes of nickel and iron. Arene type ... 

D. Baudry and M. Ephritikine, /. Organomet. Chem., 1980, 195, 213. Reactions of Cp2ReH and its derivatives. Preparation of new dicyclopentadienyl complexes of rhenium. 

For this purpose, the catalyst has to possess optimum thermodynamic parameters, for example, the redox potential corresponding to this process. As shown in practice, metal complexes with different structures are characterized by a very broad range of values. For example, for dicyclopentadienyl complexes of transition metals, depending on the nature of the central atom, the value ranges from -3 to +2 eV. The change in the donor-acceptor properties of substituents in the cyclopentadiene ring of ferrocene changes E by several electron volts. 

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