Heterobimetallic Alkoxides [CdIIMV(OiPr)7]2 (M = Nb, Ta) as Potential Precursors to Pyrochlore Cd2M2O7

Abstract

Attempts to synthesize Cd–M (M = Nb, Ta) heterobimetallic complexes by salt metathesis reaction resulted in the unexpected structural motif [I2CdII2MV(OiPr)7]2 [M = Nb (2), Ta (3)]. Multinuclear NMR analysis revealed the coexistence of multiple products in solution. Donor solvents influenced the formation of different intermediate species in solution, as was proven by 113Cd NMR spectroscopic data. The isolation of trimetallic [I2Cd{Ta(OiPr)6}K(HOiPr)2]4 (4) and the adduct [I2CdTa(OiPr)5(thf)] (5) provided insight into the reaction mechanism. By exploiting the Lewis acidic nature of cadmium alkoxides, different compounds could be synthesized and thoroughly characterized by spectroscopic methods and single‐crystal X‐ray diffraction studies. Heterobimetallic compounds with the formula [CdIIMV(OiPr)7]2 [M = Nb (6), Ta (7)] produced pyrochlore phases from an amorphous ceramic homogenate, which indicates their potential as single‐source precursors, as was confirmed by thermogravimetric/differential thermal analysis, which showed that complexes 6 and 7 undergo facile two‐step thermal decomposition at 600 °C to produce Cd2Nb2O7 and Cd2Ta2O7, respectively. Variable‐temperature X‐ray diffraction analysis of 6 additionally proved the formation of crystalline Cd2Nb2O7 phase.