Di- and Triphenylacetates of Lanthanum and Neodymium. Synthesis, Structural Diversity, and Application in Diene Polymerization

A new family of lanthanide complexes with di- and triphenylacetate ligands was prepared from LnCl3. Dimeric diphenylacetates were the only isolated products of the reaction between LnCl3 (Ln = La, Nd) and Ph2CHCOONa. The exchange reaction between LnCl3 and Ph3CCOONa 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 κ2- and κ1-terminal coordination, μ2-κ1:κ1-bridging, and μ2-κ1:κ2-semibridging. The treatment of La and Nd tris-triphenylacetates with excess AlEt3 produces the dimeric tetraethylaluminates [Ln2((μ2-κ1:κ1-Ph3CCOO)4(AlEt4)2]. 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)4Nd2(Ph2CHCOO)2(μ2-κ1:κ2-Ph2CHCOO)2(μ2- κ1:κ1-Ph2CHCOO)2] 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.