Transition-metal layered perovskites were synthesized by topotactic methods. Compounds of the approximate formula M0.5UM2O7 (M = Fe, Ni) were obtained directly by ion exchange between RbLaNb2O7 and MBr2 at low temperature (350 degreesC). Cu0.5LaNb2O7 was synthesized by another route where CUCl2 was topochemically deintercalated from (CuCl)LaNb2O7 at 550 degreesC under a dynamic vacuum. The series M0.5LaNb2O7 (M = Fe, Ni, Cu) is isostructural with adjacent double-perovskite layers aligned, as in RbLaNb2O7. The set of compounds all exhibit Curie-Weiss paramagnetism. (C) 2004 Elsevier Ltd. All rights reserved.