An unexpected trimanganese(I) tetrathiolate-bridged complex, [Mn-3(CO)(9)(mu -SC6H5)(4)](-), with an incomplete cubane structure, was obtained by thermal reaction of [Mn-2(CO)(10)] with [Mo(eta (5)-C5H5)(2)(SC6H5)(2)]. The structure, established by single-crystal X-ray diffraction studies, shows the cation, [Mo(eta (5)-C(5)H5)(2)(H)CO](+), directed towards the vacant site of the cubane structure. Possible routes by which the anion and the cation could be formed are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.