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.