Reaction of the trivacant heteropolyanions A, α-, A, β-SiW9, A, α-, A, β-GeW9 with Ln(NO3)3.xH2O leads to the formation of the rare earth derivatives A, α-, A, -β[Ln3O3.(X2W9O34)2]^1^7^-(Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Er). The complexes have been characterized by elemental analysis, IR, UV and 183W NMR spectra. Their magnetic susceptibility and their electrochemical properties have been determined.

Key words: OXIDATION REDUCTION REACTION, INFRARED SPECTROPHOTOMETRY, HETEROPOLYACID, NMR SPECTROMETRY, SILICIC ACID P, THERMOGRAVIMETRY, MAGNETISM, TUNGSTIC ACID P, GERMANIC ACID