Pyridinium hexachlorocerate

Tetrakis-cyclopentadienyl cerium (CeCp4) has been reported to be formed by the reaction of bis(pyridinium) hexachlorocerate with sodium cyclopentadienide [17]. Similarly indenyl and fluorenyl derivatives were prepared. Later work showed the same reactants in tetrahydrofurane to yield, Ce(Cp3), tricyclopentadienyl cerium complex instead of Ce(Cp4) [18]. 

The complex Cp3Ce(IV)Cl has been synthesized by reacting NaCp and bis(pyridinium) hexachlorocerate in THF. It may also be obtained [56] by the reaction of bis(pyridinium) hexachlorocerate and Cp4Ce. These compounds, Cp3CeCl may be used to prepare other compounds [57] like Cp3CeX, where X = alkyl, aryl, pseudohalide, mercaptide, carboxylate. 

Ce, with a variety of organic ligands (such as Cp or cyclotetraenyl COT) or inorganic ones (such as Oi-Pr), the syntheses being carried out from pyridinium hexachlorocerate or [Ce(0-iPr)4.i-Pr0H]. 

The synthesis of tetrakis- (or tetra-) cyclopentadienyl cerium was reported first by reaction of bis(pyridinium)hexachlorocerate and sodium cyclopentadienide (Kalsotra et al. 1971) the same reaction has been extended to other Ji-ligands such as indenyls and fluorenyls. However, in 1983 it was reported that the reaction of sodium cyclopentadienide with bis(pyridinium)hexachlorocerate in THF yields tricyclopentadienyl cerium(III) instead of tetrakiscyclopentadienyl cerium(IV) (Deacon et al. 1983). 

X=halide. Triscyclopentadienyl cerium(IV) chloride has been prepared by reaction of sodium cyclopentadienide and bis(pyridinium)hexachlorocerate in THF or benzene, or by ligand redistribution between bis(pyridinium)hexachlorocerate and tetracyclopentadienyl cerium (Kalsotra et al. 1971). These brown compounds, described as stable in water, act as starting materials for Cp CeZ (Z = alkyl, aryl, pseudohalide, mercaptide, carboxylate) (Marks and Ernst 1982). 

Hexachlorocerates(lV) stabilized by bulky Group 15 cations are easily prepared as shown in Scheme 4 starting with hydrated cerium dioxide. Among these, especially the bright yellow pyridinium salt (pyH)2 [Cede] has frequently been employed as alternative Ce(fV) precursor. ... 

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