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Cp2M + complexes, structures electronic

Metallocene complexes of Ti, Zr, and Hf have attracted considerable attention in recent years because of their high activity and since their ligand framework can be tailored to a wide variety of polymerization requirements.102 The active species is the 14-electron cationic alkyl [Cp2M—R]+, with a pseudo-tetrahedral structure and a vacant site suitable for forming a weak complex with ethylene. Calculations show that the alkyl transfer to ethylene is stabilized by an a-agostic interaction with the metal, with a very low (ca. 2 kJ mol-1) activation barrier 103... [Pg.1272]

A 16-electron, d° Cp2M(R)X species contains one low-lying metal-centered LUMO localized in the equatorial plane between the Cp ligands which is utilized for substrate coordination (Fig. 1) (11). Zr—X r-bonding (X = OR, halide, etc.) utilizes this orbital and generally results in decreased reactivity (5). The electronic structure of a Cp2Zr(R)(L) complex is similar to that of neutral analogs, but the LUMO is stabilized by the metal... [Pg.326]

Bis(cyclopentadienyl) complexes CP2M (M = Ge, Sn, Pb) have been prepared by reaction of cyclopentadienylsodium and an appropriate dihalide in tetrahydro-furan. Electron diffraction shows that in the vapour these molecules have angular structures on account of the electron pair on the metal. In the solid state the germanium compound polymerizes within 3 h at ambient temperature, the tin compound within five days. The cyclopentadienyl groups are coordinated in a symmetrical pentahapto fashion (p. 191). Association through the rings occurs in the crystalline lead compound to give a polymeric chain structure (Fig. 4.8). [Pg.122]

We saw in 15.31 and the discussion around it that the orbitals of CH2 were topologically like those in ethylene. Each has a donor orbital of 0 symmetry and a low-lying acceptor orbital. The electronic structure of an (alkyl)(olefin)MCp2 complex is then similar to the Cp2M (carbene) ones which we have just treated. 20.47 shows the Io -tt interaction which is analogous to the tt interaction in 20.46... [Pg.603]


See other pages where Cp2M + complexes, structures electronic is mentioned: [Pg.2960]    [Pg.2959]    [Pg.167]    [Pg.206]    [Pg.211]    [Pg.47]    [Pg.347]    [Pg.63]    [Pg.397]    [Pg.398]    [Pg.206]    [Pg.435]    [Pg.597]   
See also in sourсe #XX -- [ Pg.326 ]




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Cp2M

Cp2M + complexes, structures

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