Metallocene lanthanide complex

With the ligand Csi-Pr4H, whose electron richness is comparable to that of Qp 11.15 whose steric constraints are much more demanding than that of the latter ligand, THF cannot coordinate to samarium in the metallocene, even when the synthesis is carried out in this solvent.This contrasts with the other metallocene lanthanide complexes (see the beginning of the section) such as [SmCp 2(THF)2] below (note, however, that [SmCp 2] is also known... 

The solid-state structure of the ethylaluminum oxide metallocene complex (Fig. 30) shows two trivalent samarocene units connected by an [(A EtsO ]2-ethylalumoxane ( EAO ) unit. The latter was described as an adduct of two molecules of triethylaluminum with two [AUfoO]- anions [116]. An unusual asymmetric fx-r q1 (side-on) ethyl coordination mode was observed, which previously has been found only in a small number of lanthanide complexes, i.e., (CsMeshYM/zy 1-Et)AlEt2(THF) [ 144], (C5Me5) 2Sm(THF) (fx-rj1 ijx-Et) AlEt3 (Fig. 9) [115] and (C5Me5)2Sm(THF) (/i-r]1 X-Et) (/z-Cl)AlEt2 [116]. 

The synthesis of the corresponding organolanthanide chlorides was performed by transmetallation of the dilithium salt with anhydrous lutetium or yttrium trichloride. Metallocene dichloro complexes [(/ ,Y)-Me2Si(C5H3But)((+)- -Men-Cp)]Ln(/r-Cl2)Li(OEt2)2 (Ln = Y, Lu) were synthesized by treatment of the corresponding lanthanide trichlorides with the dilithium salt of the ligand and isolated isomerically pure by crystallization from diethyl ether (Scheme 162).650... 

Obviously, many structural variations are possible in the design of ferrocene oxa-aza cryptands. Some of the oxa-azaferrocene cryptands form alkali metal and lanthanide complexes [90]. FAB mass spectrometry experiments have shown that the cryptands have strong selectivity for the potassium cation compared with Li+, Na, or Cs" " [94], In these complexes the macrocycle functions as a host, but in Mg + complexes the cation is coordinated by the amide carbonyl groups [95]. In the lanthanide complexes the metallocene moiety acts as an efficient center for radiationless deactivation of the lanthanide excited state [96]. 

Very recently, Hou and coworkers have reported that rare earth half-metallocene complexes (Figure 14.16, 85-88) activated with [Ph3C] [B(C6F5)4] afford highly active systems for syndio-specific styrene polymerization, producing sPS with high syndiotacticities rrrr > 99%) and rather narrow polydispersities (Mw/Mn = 1.29-1.55). The activity of scandium complex 85 is comparable with that for the most active titanium catalysts (1.36 x 10 g sPS/(mol Sc-h)). The neutral allyl lanthanide complexes 89-92 (Figure 14.16) in the absence of a cocatalyst are also active for the syndiospecific polymerization of styrene (rrrr > 99%), but with lower activities that are in the order... 

The proposed mechanism for the metallocene complexes of Group 5 metals and lanthanides involves the coordination of alkene to the metal hydride (51), followed... 

Marks et al. reported the co-polymerization of ethylene and 1-hexene by using ansa-type complexes of lanthanide metals [127]. Recently, bulky alkyl substituted ansa-type metallocene complexes of yttrium have been reported to exhibit high activity for the polymerization of 1-hexane. [114, 119, 128]... 

Some non-metallocene complexes of lanthanide metals such as Sml2... 

---