[en] A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mossbauer spectroscopy; samples of Pr18Li8Fe5-xMxO39 and Pr18Li8Fe5-xCoxO39 (x = 1, 2) have been studied by magnetometry. All these Compounds adopt a cubic structure (space group Pm (3) over barn, a(o)similar to 11.97 angstrom) based on intersecting < 111 > chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr-O framework. The trigonal-prismatic site in Pr18Li8Fe4RuO39 is occupied by Li+ and high-spin Fe3+. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr18Li8Fe4RuO39) or below. (C) 2009 Elsevier Inc. All rights reserved.