Lanthanum complexes, homoleptic

The structurally characterized homoleptic lanthanide tris(guanidinate) complex [(CH2)sNC(NPr )2]3 Yb was synthesized analogously by the metathesis reaction of the preformed lithium guanidinate with anhydrous YbCb in a 3 1 molar ratio in THF [30], A series of new lanthanide tris(guanidinate) complexes including the first THF-solvated tris(guanidinate) lanthanum complexes were synthesized according to Scheme 14 and fully characterized [31],... 

The homoleptic lanthanum complex (3a)sLa has also been investigated in some detail in solution by... 

An interesting class of homoleptic lanthanide complexes has become available through the use of heteroallylic diphosphinomethanide ligands. The first member of the series was the lanthanum derivative, [CH(PPh2)2]3La (59c), which was characterized by X-ray crystallography (Fig. 19) [74]. The preparation of 59c involved treatment of anhydrous lanthanum trichloride with the potassium salt of the ligand ... 

Synthetic strategies to alkoxide complexes have been covered in full by previous reviews [14]. The silylamide route proved to be an advantageous method of preparation, especially in the case of homoleptic derivatives [15]. The group (IIIA) elements - scandium, yttrium and lanthanum - are considered as lanthanides on the basis of their general chemical similarity to the true lanthanides. 

The ROP of TMC using the homoleptic lanthanide amidinate complexes [RC(NCy)2]3Ln (R = Me, Ph Ln = La, Nd, Sm, Yb) as single-component initiators was investigated in detail. It was found that the substituents on the amidinate ligands and the metal centers had a great effect on the catalytic activities of these complexes, that is, Me > Ph, and La > Nd > Sm > Yb. Thus, the lanthanum acetamidinate [MeC(NCy)2]3La showed the highest catalytic activity [64]. 

The tetranuclear [La (OC2H4)3N 2 Nb(OPr )4 3] contains eight-coordinated (bicapped trigonal antiprism) La and distorted octahedral niobium (Fig. 4.62). ° A homoleptic trinuclear lanthanum niobium complex [(Pr 0)3Nb(/t-OPr )3La(OPr )(/t-OPr )2Nb(OPr )4] has also been established. The distorted octahedral La is triple-bridged to one Nb and double-bridged to the other, generating a bent (136.2°) NbLaNb axis." ... 

The first structurally characterized homoleptic trialkyllanthanoid complex has been obtained when lanthanum phenoxide was used as the initial compound in the reaction with RLi [40] ... 

The promising results obtained with Sn(Oct)2, Al(Oi-Pr)3 and Zn(Lact)2 have stimulated the evaluation of a number of homoleptic complexes featuring alkoxy and carboxy ligands [2bj. As representative examples, trivalent yttrium and lanthanum alkoxides Ln(OR)3 (Ln = La, Y and R = i-Pr, n-Bu) have proved to be much more active than the related aluminum alkoxides, and to efficiently promote the... 

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