Yttrium complexes mono

Wang, Z.G, Sun, H.M., Yao, H.S. et al. (2006) Mono- and tris-phenoxo-tethered N-heterocyclic carbene yttrium complexes syntheses and molecular structures. Organometallics, 25, 4436. 

In 1999, An wander et al. synthesized the first rare-earth metal complexes containing bisoxazolinate ligands [132]. Yttrium and lanthanum were chosen as examples for small and large rare-earth metal centers to show the high scope of the synthesis. Both types of complexes, mono-bisoxazolinates and bis-bisoxazolinates. 

These dimers are less reactive or unreactive in catalytic reactions of interest, and thus some substitution on the cyclopentadienyl ligands is necessary to prevent dimer formation through steric hindrance to association. Pentamethylcy-clopentadienyl (Cp ) ligands are useful for this, and lead to catalytic systems that are highly reactive and yet exquisitely selective in the insertion of mono-substituted alkenes. One such precatalyst system is the yttrium complex Cp 2YMe THF. Although Lewis bases normally depress catalytic activity because they compete for empty coordination sites on the catalyst, in this precatalyst the single THF of solvation appears to catalyze the hydrometallation process [Eq. (5)] [15] in the same manner that Lewis bases catalyze the hydroboration of olefins with 9-BBN [16] ... 

Aryloxo-NHC-containing complexes could also be produced from amido precursors where the ligands also acted as internal base as shown by the Shen group. Hence, a hydroxyaryl-imidazolium ligand reacted with [LiY N(z-Pr2) 4] and BuLi at — 78 °C to give the NHC-yttrium complex [(NHQ3Y] 21 (Scheme 6.2). " From [LiYb N(z -Pr2) 4], a bis-substituted ytterbium compound [(NHC)2Yb N(z-Pr2) ] 22 was prepared. Of note, all attempts to prepare the mono-substituted complex were unsueeessful. 

Mono(guanidinate) complexes of lanthanum and yttrium have been synthesized as illustrated in Scheme 58.The lanthanum compounds were made starting from La[N(SiMe3)2]3 and dicyclohexylcarbodiimide. Both mono (guanidinate) derivatives are monomeric in the solid state with a four-coordinate La center. ... 

The guanidinate-supported titanium imido complex [Me2NC(NPr02l2Ti = NAr (Ar = 2,6-Me2C6H3) (cf. Section IILB.2) was reported to be an effective catalyst for the hydroamination of alkynes. The catalytic activity of bulky amidinato bis(alkyl) complexes of scandium and yttrium (cf. Section III.B.l) in the intramolecular hydroamination/cyclization of 2,2-dimethyl-4-pentenylamine has been investigated and compared to the activity of the corresponding cationic mono(alkyl) derivatives. 

Structural evidence of the generation of mono- and dicationic alkyl species was reported by J. Okuda and coworkers [155,269]. Monoca-tionic yttrium(III) dimethyl and dicationic yttrium(III) methyl complexes, [YMe2(THF)5][BPh4] and [YMe(THF)6] [BPlLk, respectively, were synthe-... 

Scheme 67 Synthesis of mono- and dicationic yttrium methyl complexes from Y(AlMe4)3 and [NEt3H][BPh4] [269]...

Attempts to synthesize the clathrochelate complexes of lanthanide ions via template condensation of the tripodal amine tren with formaldehyde bis-(dimethylamino)methane derivative on the rare-earth metal ion were successful only for ytterbium. The [Yb(metr)](CF3S03)3 AN clathrochelate was obtained in 3-5% yield [165]. With ytterbium cation, as well as with cerium, praseodymium, europium, yttrium, and lanthanum ions, the major reaction products proved to be mono- and dibridged semiclathrochelate complexes with ligands 1 and 2 (Scheme 71). 

The bis(oxoazoline) ligand (4) acts as a bidentate ligand with yttrium.131 The reaction of 2,2 -methylene-bis[(4S)-4-/er/-butyl-2-oxazolinc with Y[N(SiHMe2)2]3(thf)2 gave the mono or bis-oxoazoline complexes, [(oxoazoline)Y N(SiHMe2)2 2] or [(oxoazoline)2YN(SiHMe2)2]. 

Scheme 13 Synthesis of the mono- and dicationic yttrium methyl complexes 33 and 34 from yttrium aluminate 31 or hexamethyl yttrium 32...

Mono(guanidinato) complexes of lanthanum and yttrium were synthesized as illustrated in Scheme 32 [6,7]. 

In a follow up report from Zi s group [52c], a very related set of two more yttrium mono- and bis(amidate) complexes were reported for their ROP reactivity. Not surprisingly their reactivities as initiators led to very similar polylactide formation, however with slightly less control over the stereoregularity of the polymer. 

Mono Cp zirconium, yttrium, and titanium complexes have also been employed, which typically give 50—60% trans rings. The catalyst formed from CpZrCls gives polymer with 80% trans rings, (a) Cavallo, L. Guerra, G. Corradini, P. Resconi, L. Waymouth, R. M. Macromolecules 1993, 26, 260—267. (b) Schaverien, C. J. Organometalllcs 1994, 13, 69—82. (c) Jeremic,... 

The only other class of compound that contains a lanthanide(III) ion and one [8]annulene ligand is the "mixed sandwich" complex, the [8]annulenelanthanate(III) cyclopentadienides. s This class of complexes can be made either by the addition of cyclopentadienide to the mono-[8]annulenelanthanide chlorides or by the addition of [8]annulene dianion to cyclopentadienyllanthanatedll) dichloride. The yttrium a and scandium members of this class have also been reported. 

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