Yttrium complexes hydride dimer

Synthesis and reactivity of the yttrium hydride dimer [Cp Y(OAr)(/i-Fl)]2 (Ar = 2,6-Bu2C6H3) have been investigated in detail.294 295 Synthetic routes leading to tetranuclear yttrium and lutetium hydride clusters have been worked out. The complexes are accessible by reacting precursors of the type (CsMe4SiMe2R)Ln(CFI2SiMe3)2(TF[F)... 

The dimeric dicyclopentadienyl methyl yttrium complex reacts readily with methyl aluminum dichloride with loss of the methyl group and formation of a stable di- u-chloro-bridged dicyclopentadienyl yttrium dimethyl aluminum complex (Holton et al., 1979c), and dicyclopentadienyl yttrium chloride reacts with aluminum hydride in ether with formation of a white crystalline 2 1 1 complex, of which the X-ray structure was determined (Lobkovskii et al., 1982) ... 

The hydrides 44b have been found to polymerize ethylene and react with a variety of protic reagents such as terminal alkynes and nitriles. Catalytic effects in the hydroboration of olefins have also been observed [27]. A well-defined /i-ethynyl complex of yttrium is formed by protolysis of the alkyl derivative 38b with acetylene (Eq. 18). Figure 14 shows the dimeric structure of 45b with bridging ethynyl ligands [27, 65]. 

The dissociation of the dimer [Cp 2Y(/i-H)]2 to the Cp 2YH monomer is an important process in the reactions of the dimer with alkenes. The kinetics and formation of yttrium alkyl complexes from [Cp 2Y(//-I I)]2 and alkenes have been investigated.587 In situ prepared dimeric bis(pentamethylcyclopentadienyl)yttrium hydride reacted rapidly with 3,3-dimethyl-l,4-pentadiene in methylcylohexane-r/ at — 78 °C and formed a bright yellow solution of the t/°-yttrium(m)pentenyl chelate complex Cp 2Y[7/,7/2-CI I2CI I2CMc2CI I=CH2] in 98% yield (Scheme 130). This pentenyl chelate complex was also prepared in toluene-// in 84% yield. The chelate complex was stable for about 2 weeks at — 78 °C but decomposed after a few hours at —50 °C. The complex was characterized without isolation by 1H and 13C NMR spectroscopy at —100 °C such complexes can be regarded as models for the coordination of alkenes to lanthanide and isoelectronic grouop 4 polymerization catalysts.588 Agostic interactions in yttrium alkyls of the type... 

The reaction of (C9H7)2LnCl(THF) with NaH in THF generates the dimeric bis(indenyl)lanthanide hydrides [(C9H7)2Ln(/r-H)]2 4THF-NaCl.695 The stereoselective synthesis and structural characterization of raf-planar chiral bis(2-methoxyethylindenyl)lanthanum and yttrium tetrahydroborate complexes has been achieved. The complexes... 

The dimeric yttrium and samarium hydride complexes are converted into monomers in the first step of the reaction. The preparation of block-co-polymers of 1-hexene or 1-pentene with MMA and e-caprolactone, respectively, has also been reported. The polymerization of ethylene with MMA, e-caprolactone and 2,2-dimethyltri-methylenecarbonate was studied in detail racemic Me2Si(CsH2-2-SiMe3-4-But)2Sm(THF)2 or meso-Me2Si(Me2SiOSiMe2)(CsH2-3-But)Sm(THF) were active in the ABA-type triblock-co-polymerization.986... 

A unique example of non metallocenic catalyst [(DADMB)YMe], [(DADMB) = 2,2 -bis(/er -butyldimethylsilylamido)-6,6 -dimethyldiphenyl], was recently reported [13]. It was assumed that the methyl complex first reacts with the silane to give a small concentration of a monomeric highly reactive hydride (Scheme 2). The yttrium hydride was not detected by NMR spectroscopy, probably because its concentration is very low. Nevertheless, precipitation of the insoluble yttrium dimer [(DADMB)YH]2 occurred at the end of the reaction. The bulky ligand... 

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