Cyclopentadienyl compounds synthesis

One path of research resulting from the discovery of ferrocene has been concerned with the synthesis and structural elucidation of cyclopentadienyl derivatives of other metals and metalloids. At the present time, over 60 chemical elements have been found to form one or more cyclopentadienyl compounds. This topic has recently been reviewed by the present author as well as by others (17, 83, 125). 

The reaction of metal cyclopentadienyl compounds with organosilicon electrophiles has been the most widely applied method for the synthesis of silylated cyclopentadienes (see Scheme 3) since the beginning of cyclopentadienylsilicon chemistry1. 

Cyclopentadienyl compounds of lithium, sodium, potassium, magnesium and thallium are most commonly used. The synthesis of these cyclopentadienyl-transfer agents is described in more detail in Section II.B.2. Organosilicon halides and alkoxides are the most convenient substrates. The synthesis of side-chain functionalized cyclopentadienyl silanes is described in equation 541,42 as a typical example of this strategy. 

Mono(cyclooctatetraenyl) lanthanide(III) compounds, synthesis and characteristics, 4, 124 Mono(cyclooctatetraenyl) zirconium(III) compounds, preparation and reactions, 4, 743 Mono(cyclopentadienyl) amido complexes alkane elimination, 4, 446 amine elimination, 4, 442 HCL elimination, 4, 446 metathesis reactions, 4, 438 miscellaneous reactions, 4, 448 properties, 4, 437... 

J. M. Birmingham, Adv. Organomet. Chem., 2,36S (1964). Excellent review of the first 10 years of transition-metal-cyclopentadienyl complex synthesis, including a tabular survey of known compounds to June, 1963. 

It is becoming apparent that nonbonding interactions play a greater role than previously appreciated in determining the structures of both main-group and transition-metal metallocenes. Molecular mechanics are particularly efficient in describing such interactions and can be readily applied to much larger systems than traditional MO methods. The analysis of structural conformations of bis(cyclopentadienyl) compounds used in stereoselective synthesis can be expected to benefit from wider applications of MM methods. 

The only known Tl1 organo compound is the polymeric T1C5H5 precipitated on addition of aqueous TIOH to cyclopentadiene InC5H5 is similar. In the gas phase these compounds consist of discrete molecules having five-fold symmetry. The metal atoms lie over the centers of the rings and are apparently bound by forces mainly of covalent nature. T1C5H5 is a very useful reagent for the synthesis of other metal cyclopentadienyl compounds (Chapter 23). 

Cyclopentadienyl compounds. An inq)roved synthesis of CpNa has been rqrarted. Crystal structures have been determined for the following cyclopentadiMiyl-metal species (i)... 

Cyclopentadienyl compounds belong to the most commonly utilized organome-tallic derivatives in various areas of chemistry and technology. They are commonly utilized in organic synthesis.Ferrocene derivatives containing asymmetric sub-... 

Synthesis of cyclopentadienyl compounds of metals from cyclopentadiene depends on the strongly acidic properties of cyclopentadiene. This acidity may be attributed to the ready formation of the highly resonance-stabilized cyclopentadienide anion, CsHs , in which there are six delocalized ir electrons. This method is limited primarily to the active metals of Groups lA and IIA and to their strongly basic compounds. The compounds produced are principally the ionically bonded metal cyclopentadienides. 

The reaction of the ionic cyclopentadienides with metal compounds is by far the most general method for synthesis of cyclopentadienyl metal compounds. This method is applicable both to transition metals, which form 7T-bonded cyclopentadienyl compounds principally, and to main group metals which form a-bonded cyclopentadienyl compounds. 

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