Cyclopentadienyls indenyls

Figure 10.20. Cyclopentadienyl-indenyl zirconium catalyst for hemispecific polymerisation...

Attempts have been made to observe1084 the assumed interconversion of 625 to 626 in fluorenyl cations. Such intramolecular interconversion through the capped pyramidal ion 627 was not observed [Eq. (3.150)]. MINDO/3 calculations1084 on the isomeric structures of cyclopentadienyl, indenyl, and fluorenyl cations indicated strongly decreasing relative stabilities of pyramidal forms due to bezannulation. 

In his classical review, Stucky (1) has already mentioned that in many n complexes the position of the lithium-base fragment is determined by the interaction of the frontier orbitals in the n fragment with the relevant orbitals at the lithium atom. This is nicely demonstrated by a series of cyclopentadienyl-, indenyl-, and fluorenyllithium complexes containing two further nitrogen atoms coordinated to the lithium as portrayed in Figs. 1 and 2. 

Organic fragments which can serve as n ligands include cyclopentadienyl, indenyl, and fluorenyl systems as well as polynuclear aromatic anionic and dianionic species. From IR and NMR data it has been concluded that the bonding in these complexes may be regarded as fully ionic. 

A cyclopentadienyl, indenyl-ethane ligand undergoes insertion altematingly in an isotactic and an atactic fashion to give a hemitactic polymer, as is to be expected. 

Region A In going from the anthronyl, tetraphenyl-cyclopentadienyl, indenyl, and fluorenyl to the diphenyl group, ty2 increases steadily. 

Lanthanide indenyl complexes of Ln(III) are known. Ce(IV), Sm(II) also form indenyl complexes. Mixed cyclopentadienyl-indenyl complexes of lanthanides have been prepared by reacting CpLnCl with NaC9H7. Typical preparation involves the reaction [221]... 

CpLi exists in ethers as a contact ion pair, in which the lithium ion is located above the cyclopentadienyl ring. The crystal stmcture of CpLi(12-crown-4) reveals analogous stmctural features. This complex has a sandwich-type stmctnre in which the lithium ion is coordinated to the fonr oxygen atoms of the crown ether on one side and to the Cp ring on the other. Several X-ray stmctnres of alkah metal cyclopentadienyl compounds containing silyl snbstitntion of the Cp ligand have been reported. The stmctnres of fluorenyl alkali metal complexes (Li-Cs) stabilized by diglyme have also been reported. The crown-ether-stabUized compounds of cyclopentadienyl, indenyl, and flnorenyl with the heavier metals, Rb and Cs, have also been reported. A common stmctural feature is the if coordination of... 

Allyl, Cyclopentadienyl, Indenyl, and Tris(Pyrazolyl)Borate Complexes... 

ALLYL, CYCLOPENTADIENYL, INDENYL, AND TRIS(PYRAZOLYL)BORATE COMPLEXES... 

Mc2 Si-bridged cyclopentadienyl/indenyl (donor-func-tionalized)-an5 a-metallocenes Mc2 Si(C5 H2-3,5- BuMe)-... 

T-acetylide ruthenium complexes with the [Ru (ri -C5R5)L2] fragment (C5R5 = cyclopentadienyl, indenyl L2 = mono- or bisphosphines) as the electron donor group. These complexes display in the visible intense MLCT absorptions, which dominate the (3 responses, and, compared with... 

Four of the catalysts presented in Figure 11 contain unsubstituted cyclopentadienyl, indenyl, or fluorenyl ligands. Of these, 1, 2, and 3 represent well-known examples of catalysts producing syndiotactic, isotactic, and hemiisotactic polypropene at low temperatures, respectively, and we will thus start our analysis of the theoretically derived pentads by comparing... 

In most cases the catalyst precursor is a metallocene dichloride complex consisting of two aromatic five-membered ring systems that can be tethered by a bridging unit ansa metallocene complexes) or not. The two aromatic ligands at the metal can be of the same type. i.e.. cyclopentadienyl. indenyl. or fluorenyl. The introduction of substituents at certain positions of the two aromatic ligands and/or the bridge modifies not only the steric and electronic conditions in the molecule but also the symmetry of such a metallocene dichloride complex. Another variable parameter is the metal M = Ti. Zr. Hf. 

Copper N-heterocyclic carbene complexes in catalysis 13CST912. Cyclopentadienyl-, indenyl- and fluorenyl-fimctionalized N-hetero-cyclic carbene metal complexes Synthesis and catalytic applications 12EJI1309. 

As mentioned in Sect. 3.1.1, Green has described a variety of homo- and heterobimetallic complexes containing a methylene-bridged (cyclopentadienyl)(indenyl) ligand [80]. The Co/Zr heterobimetallic complex 46 has been examined as catalyst precursor for ethylene polymerization with MAO as cocatalyst and shows activities similar to the Fe/Zr complex 22 or [Cp2ZrCl2]-MAO (Scheme 30). 

Related chain polymers have also been found in several Lewis-base adducts of alkali metal cyclopentadienyl, indenyl, and fluorenyl complexes. Such adducts with ethers or amines have been thoroughly investigated because they form stable, crys-... 

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