Water-Free Neodymium 2,6-Naphthalenedicarboxylates Coordination Complexes and Their Application as Catalysts for Isoprene Polymerization

A series of four coordination polymers based on neodymium
have
been hydrothermally synthesized with different carboxylic acids as
a linker. The structures of the compounds Nd2(2,6-ndc)3(H2O)3·H2O (1), Nd2(2,6-ndc)2(ox)­(H2O)2 (2), and Nd­(2,6-ndc)­(form) (3) (2,6-ndc
= 2,6-naphthalenedicarboxylate; ox = oxalate; and form = formate)
have been determined by single-crystal X-ray diffraction analysis.
They exhibit rather dense networks built up from infinite chains of
NdO polyhedra connected to each other through the 2,6-ndc ligand.
Terminal and bridging aquo species are present in the coordination
sphere of Nd for 1, whereas some of them are partially
replaced by oxalate groups in 2 and fully substituted
by formate groups in 3. The water-free phase 3 as well as the compound Nd­(form)3 (4) were
considered for catalytic reaction for polymerization of isoprene in
the presence of Al-based cocatalyst, affording cis-polyisoprene with good conversions.
Residual Nd material with unchanged structure was found in the polymeric
material. The neodymium luminescence of compounds 3 and 4 was also measured.

本研究以不同羧酸为连接配体，通过水热法合成了一系列共4种钕基配位聚合物。化合物Nd₂(2,6-ndc)₃(H₂O)₃·H₂O（1）、Nd₂(2,6-ndc)₂(ox)(H₂O)₂（2）与Nd(2,6-ndc)(form)（3）的结构经单晶X射线衍射分析得以解析（其中2,6-ndc为2,6-萘二甲酸根(2,6-naphthalenedicarboxylate)，ox为草酸根(oxalate)，form为甲酸根(formate)）。上述化合物均构建为由NdO多面体无限链构成的致密网络，链间通过2,6-ndc配体相互连接。化合物1中钕的配位球内同时存在端基配位与桥联配位的水物种；化合物2中部分水物种被草酸根取代，化合物3中则全部被甲酸根取代。将无水相的化合物3与化合物Nd(form)₃（4）作为催化剂，在铝基助催化剂存在下用于异戊二烯聚合反应，可得到转化率优异的顺式聚异戊二烯，且聚合产物中可分离得到结构未发生改变的含钕残余物料。此外，还对化合物3和4的钕元素发光特性进行了表征测试。