Influence of Schiff Base and Lanthanide Metals on the Synthesis, Stability, and Reactivity of Monoamido Lanthanide Complexes Bearing Two Schiff Bases

Abstract

The monoamido lanthanide complexes stabilized by Schiff base ligand L(2)LnN(TMS)(2) (L = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-8-C(9)H(6)N, Ln = Yb (1), Y (2), Eu (3), Nd (4), and La (5)) were synthesized in good yields by the reactions of Ln[N(TMS)(2)](3) with 1.8 equiv of HL in hexane at room temperature. It was found that the stability of 1-5 depends greatly on the size of the lanthanide metals with the increasing trend of Yb ≈ Y < Nd < La. The amine elimination of Ln[N(TMS)(2)](3) with the bulky bidentate Schiff base HL' (L' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Pr(i)(2)-C(6)H(3)) afforded the monoamido lanthanide complexes L'(2)LnN(TMS)(2) (Ln = Yb (9), Y (10), Nd (11), and La (12)). While the amine elimination with the less bulky Schiff base HL'' (L'' = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-2,6-Me(2)-C(6)H(3)) yielded the desired monoamido complexes with the small metals of Y and Yb, L''(2)LnN(TMS)(2) (Ln = Yb (13) and Y (14)), and the more stable tris-Schiff base complexes with the large metals of La and Nd, yielded L''(3)Ln as the only product. Complexes 1-14 were fully characterized including X-ray crystal structural analysis. Complexes 1-5, 10, and 14 can serve as the efficient catalysts for addition of amines to carbodiimides, and the catalytic activity is greatly affected by the lanthanide metals with the active sequence of Yb < Y < Eu ≈ Nd ≈ La.

A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

“…Compounds of lanthanides and iron containing the tridentate [O,N,N] salicylaldiminato ligands have been utilized for the ROP of rac-LA and L-LA but to the best of our knowledge investigations of ROP using complexes derived from this ligand containing group 4 metals remain completely unexplored [125][126][127].…”

Structural and Mechanistic Insights into s‐Block Bimetallic Catalysis: Sodium Magnesiate‐Catalyzed Guanylation of Amines

“…[9] The vast majority of theses tudies have focusedo nt ransition-metal and rare-earth-metalc atalysis. [14] Notwithstanding, some recent studies of lithium [15, 16a] or magnesium (and heavier Group 2e lements) [16,17] have already demonstratedt he potential of s-blockm etal complexes to catalyze these reactions. Relateds tudies that investigated the synthesis of phosphaguanidines have revealed the ability of heavier alkaline-earthmetal amides to catalyzet he direct addition of secondary phosphines to carbodiimides.…”

Synthesis, Structure, and Reactivity of Homodinuclear Lanthanide Complexes Bearing Salen‐type Schiff‐base Ligand

“…In complex 2 , the Nd–N(imine) distances range from 2.565(7) to 2.609(6) Å. The average Nd–N(imine) distance of 2.597(6) Å is longer than those in the previously reported neodymium Schiff‐base complexes, [3, 5‐ t Bu 2 ‐2‐(O)‐C 6 H 2 CH=N‐C 5 H 4 N] 2 Nd‐[N(TMS) 2 ] [2.551(3) Å],16 [3, 5‐ t Bu 2 ‐2‐(O)C 6 H 2 CH=N‐8‐C 9 H 6 N] 2 Nd[N(TMS) 2 ] [2.557(6) Å],7a and [N{CH 2 CH 2 N=CH(2‐O‐3, 5‐ t Bu 2 C 6 H 2 )} 3 ]Nd [2.587(6) Å],17 but slightly shorter than that in the tris(salicyladiminato) neodymium complex [3, 5‐ t Bu 2 ‐2‐(O)‐C 6 H 2 CH=N‐C 6 H 5 ] 3 Nd(THF) [2.696(6) Å], if a subtraction of the difference between six‐ and seven‐coordinate Nd 3+ in radii is made. These results reflect the fact that the coordination of three Schiff‐base ligands increases the steric congestion around the neodymium atom.…”