Tetramethylcyclopentadienyl ligands

Giesbrecht, G.R., Cui, C.M., Shafir, A. etal. (2002) Divalent lanthanide metal complexes of atriazacyclonoane-functionalized tetramethylcyclopentadienyl ligand X-ray crystal structures of [C5Me4SiMe2( Pr2-tacn)]Lnl (Ln=Sm, Yb tacn=l,4-diisopropyl-l,4,7-triazacyclononane). Organometallics, 21, 3841. 

The synthesis and characterization of divalent lanthanide complexes of a triazacyclononane-functionalized tetramethylcyclopentadienyl ligand have been reported.200 201 Addition of LnI2(THF)2 (Ln = Sm, Yb) to K[CsMe4SiMe2(Pr 2-tacn)] (Pr 2-tacn = l,4-diisopropyl-l,4,7-triazacyclononane) in THF yielded the monomeric organolanthanide [CsMe4SiMe2(Pr 2-tacn)]SmI (dark red crystals, 85% yield) and [C5Me4SiMe2(Pr 2-tacn)]YbI (red blocks, 80% yield) (Scheme 40). The crystal structures of both compounds have been explored.200... 

A PtMe complex with a tetramethylcyclopentadienyl ligand, having a 2-(dimethylamino)ethyl group, and with cod as a monodentate ligand 410, reacts with PMe3 to afford a complex whose metal center is bonded to a cyclooctenyl ligand via a- and vr-bonds 411 (Equation (103)). ... 

Extensive efforts have also been made to develop olefin polymerisation catalysts based on metallocenes with only one ligand of the cyclopentadienyl type. Ethylene-,dimethylsilylene- or tetramethyldisilylene-bridged mono(l-tetra -methylcyclopentadienyl), mono(l-indenyl) or mono(9-fluorenyl)-amidotita-nium complexes, such as dimethylsilylene(l-tetramethylcyclopentadienyl)(t-butyl)amidotitanium dichloride [Me2Si(Me4Cp)N(/-Bu)TiCl2] (Figure 3.10), have recently attracted both industrial and scientific interest as precursors for methylaluminoxane-activated catalysts, which polymerise ethylene and copolymerise ethylene with 1-butene, 1-hexene and 1-octene [30,105,148-152]. 

Yb(THF)]2 (Figure 108b) containing the heterobiftmc-tional tetramethylcyclopentadienyl-silanolate ligand has also been reported. 

The divalent lanthanide monohalides, which are suitable precursors for mixed-ligand divalent lanthanide complexes, can also be synthesized via metathesis reaction. For example, the divalent samarium and ytterbium monohalides stabilized by a triazacyclononane-functionalized tetramethylcyclopentadienyl group have been prepared (Equation 8.31) [97]. 

Figure 10.8 Synthesis of iron(II) complexes bearing tetramethylcyclopentadienyl-functionalized NHC ligands.

Lanthanum (La) and lanthanide metals neodymium (Nd), samarium (Sm) and lutetium (Lu) as well as yttrium (Y) with pentamethylcyclopentadienyl (// -MesCs = Cp ) and a silicon-bridged bis(tetramethylcyclopentadienyl) (Me4C5-SiMe2-C5Me4 = Me2SiCp"2) ligand have been proved to be excellent and unique hydrosilylation catalysts which exhibit distinctive features in comparison with traditional Group VEEI late-transition metal catalysts" "". ... 

Phosphanylalkyl/aryl)tetramethylcyclopentadienyl complexes of rhodium 84 were obtained from lithiated 1,2,3,4-tetramethyl-5-(2-P,P-dialkyl/arylphosphinoethyl)cyclopentadiene and [Rh(/r-Cl)(CO)2]2. The electron-donating properties of these ligands were compared to the related (phosphanylalkyl/aryl)cyclopentadienyl complexes 85. The P-Rh bond is shown to be stable under methanol carbonylation reaction conditions. ... 

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