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

摘要

Attempts to synthesize Cd-M (M = Nb, Ta) heterobimetallic complexes by salt metathesis reaction resulted in the unexpected structural motif [(I2Cd2MV)-M-II(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 Cd-113 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 [(CdMV)-M-II( 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 degrees C to produce Cd2Nb2O7 and Cd2Ta2O7, respectively. Variable-temperature X-ray diffraction analysis of 6 additionally proved the formation of crystalline Cd2Nb2O7 phase.