Di- and Triphenylacetates of Lanthanum and Neodymium.
Synthesis, Structural Diversity, and Application in Diene Polymerization
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Abstract
A new
family of lanthanide complexes with di- and triphenylacetate
ligands was prepared from LnCl<sub>3</sub>. Dimeric diphenylacetates
were the only isolated products of the reaction between LnCl<sub>3</sub> (Ln = La, Nd) and Ph<sub>2</sub>CHCOONa. The exchange reaction between
LnCl<sub>3</sub> and Ph<sub>3</sub>CCOONa led to the formation of
three structurally different types of neodymium and lanthanum complexes
under different reaction conditions. Various coordination modes of
the carboxylate ligands were revealed, including κ<sup>2</sup>- and κ<sup>1</sup>-terminal coordination, μ<sub>2</sub>-κ<sup>1</sup>:κ<sup>1</sup>-bridging, and μ<sub>2</sub>-κ<sup>1</sup>:κ<sup>2</sup>-semibridging. The
treatment of La and Nd tris-triphenylacetates with excess AlEt<sub>3</sub> produces the dimeric tetraethylaluminates [Ln<sub>2</sub>((μ<sub>2</sub>-κ<sup>1</sup>:κ<sup>1</sup>-Ph<sub>3</sub>CCOO)<sub>4</sub>(AlEt<sub>4</sub>)<sub>2</sub>]. The structures
of the key La and Nd triphenylacetates that were obtained from these
reactions were verified by X-ray diffraction, and the complex [(THF)<sub>4</sub>Nd<sub>2</sub>(Ph<sub>2</sub>CHCOO)<sub>2</sub>(μ<sub>2</sub>-κ<sup>1</sup>:κ<sup>2</sup>-Ph<sub>2</sub>CHCOO)<sub>2</sub>(μ<sub>2</sub>- κ<sup>1</sup>:κ<sup>1</sup>-Ph<sub>2</sub>CHCOO)<sub>2</sub>] was studied by high-resolution
X-ray diffraction. Neodymium di- and triphenylacetate complexes can
serve as precursors of catalysts for butadiene and isoprene stereospecific
1,4-cis polymerization
