Pentamethylcyclopentadienyl derivatives

The pentamethylcyclopentadienyl derivatives of rhodium Cp RhL (L = PMe3, C2H4) oxidatively add thiophene preferentially via the C—S activation route compared to that based on the C—H activation [880M1171,94JOM(472)311]. The Tp derivatives by contrast yield mainly the latter. Tp Rh(PEt3) acts almost selectively and forms exclusively 225 (R = Et), whereas Tp Rh(PMc3) forms a major amount of 225 (R = Me) and minor amount of 226 (960M2678). 

The uranium(III) complexes Cp2UI2(THF)3 and Cp UI2(py)3 have been structurally characterized [393b]. The similar tribromide complex Cp ThBr3(THF)3 [111] provides a convenient entry into the chemistry of mono(pentamethylcyclopentadienyl) derivatives of thorium. Aryloxide and alkyl derivatives may be readily prepared by treatment of Cp RhBr3(THF)3 with potassium aryloxide or alkyl Grignard reagents, respectively [373], for example (5.58)-(5.60) ... 

The ytterbium(III) product 14o was isolated as large colorless crystals in 33% yield. A comparable pentamethylcyclopentadienyl derivative, (C5Me5)2Yb(S2CNEt2) was described by Andersen et al. in 1982 [52]. The bent [PhC(NSiMe3)2]2Yb unit in 14o structurally resembles the bent lanthanide metallocenes containing (C5Me5)2Ln moieties (Fig. 5). 

The complex, formally derived from a double oxidative addition of benzene to two Ir centers , is in contrast to the mononuclear product obtained with the pentamethylcyclopentadienyl derivative . In the absence of light there is no reaction presumably photolysis displaces one carbonyl ligand to give a coordinatively unsaturated precursor. An apparent intermediate in the photolysis has H NMR resonances in the aromatic, cyclopentadienyl and hydride regions and may be IrGp-j/ (GO)H(G6H5), but its nature remains uncertain. 

The corresponding pentamethylcyclopentadienyl derivative (C5Me5)SbCl2, 55, was made analogously [59, 60]. The compounds have a very similar polymeric chain... 

The pentamethylcyclopentadienyl derivatives of ytterbium, (C5Me5)2Yb(h-Cl)(M,-CH3)Li(Et20)2 and (CsMes)2Yb(n-CH3)2Li(Et20)2 have been obtained by the reaction of (C5Me5)2Yb(M. "Cl)2Li(Et20)2 with methyllithium in THF (55). The corresponding lutetium derivatives. 

Pentamethylcyclopentadienyl derivatives of Sc (58) and Lu (85,86, 87) have also been prepared and investigated. The nmr spectra suggest an equilibrium between the monomeric and the dimeric species as shown for the lutetium compounds. They catalyze the polymerization of olefins and activate C-H-bonds, even those of tetramethylsilane (85,86,87) ... 

Our group started a research program on the synthesis and reactivity of Cp2TiR (R = alkyl, aryl) compounds in the early seventies, and from about 1980 on, pentamethylcyclopentadienyl derivatives, Cp TiR, were studied. Based on our experience with Group IVB and other early transition metal chemistry we decided to expand our field to Group IIIB compounds Cp MR, and for economic reasons we chose yttrium. Later... 

Pentamethylcyclopentadienyl derivatives are obtained by reaction of alkyllithiums with (77 -Gp )Ni(acac). In the presence of PMes, LiMe leads to the complex (r7 -Gp )Ni(Me)(PMe3), and with 2,4-dilithio-l,2,3,4-tetraphenyl-butadiene the internally stabilized alkenyl complex 247 is formed. The latter rearranges at 60°G to give a mixture of isomeric allyl complexes (Scheme 78). The binuclear decacyclene complex 248 readily undergoes the... 

In search for new active catalysts of the olefin polymerization over the last years several REM monocyclopentadienyl complexes containing a-bonded ligands have been synthesized (Table 1.7) [39, 58, 136-138]. Neutral derivatives of CpLnX2 as well as heterobimetallic complexes [Li(B)][CpLnCl3] have been utilized in these synthesis as the initial compounds. It should be noted that in all cases, except CpHo(C=CPh)2 obtained in 1975 [139], pentamethylcyclopentadienyl derivatives have been used. 

Pentamethylcyclopentadienyl derivatives of lanthanoids have been synthesized by the interaction of Li(CH2>2PRR with the dichloride ate-complex [236, 244]. 

The formation of a pentamethylcyclopentadienyl derivative from hexamethyl-Dewarbenzene in the presence of [PtCl ] and acid is thought to involve A -C6Me6 derivatives of platinum(n) and of... 

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