Crystal Structure of Lanthanide‐oxalate‐pyridine‐2,4‐dicarboxylate Coordination Polymers Suggesting the Reductive Coupling of Carbon Dioxide to Oxalate

Under the hydrothermal conditions, Nd(NO 3 ) 3 ·6H 2 O reacted with pyridine‐2,4‐dicarboxylic acid (2,4‐pydcH 2 ) to give a 2D co‐ordination polymer with the empirical formula of C 16 H 18 N 2 Nd 2 O 18 ×H 2 O ( 1 ). Pr(NO 3 ) 3 ·6H 2 O also reacted with 2,4‐pydcH 2 to give another 2D coordination polymer (C 8 H 9 NO 9 Pr) 2 ·H 2 O ( 2 ). The structure of both polymers have been determined by X‐ray diffraction. X‐ray structural analyses show that both polymers contain bridging oxalate (C 2 O 4 2− ) ligands, which might have been formed by the coupling of two CO 2 − × radicals, released from pydc 2− ligands.