Reactions of [PPh4][(eta(5)-C5Me5)WS3] with CuBr and EPh3 (E = As, P) in MeCN gave rise to [eta(5)-C5Me5)WS3Cu3Br2)(EPh3)(2)] (1: E = As; 2: E = P) in high yield. Single-crystal X-ray analysis revealed that the structure of 1 or 2 consists of a half-open cubane-like [WS3Cu3Br] cluster core where one Cu-Br bond is broken. The optical limiting properties for 1 and 2 in CH2Cl2 were studied with 12 ns and 35 ps laser pulses at 532 nm. The linear transmittance and thresholds at 532 nm laser light for I and 2 are 58% and 2.1 J cm(-2), and 41% and 1.9 J cm-2, respectively. The optical limiting properties of 1 and 2 are compared with those of known closed cubane-like and nest-like clusters derived from [MS4](2-), [MOS3](2-) (M = Mo, W), and [MoSe4](2-) anions. (C) 2003 Elsevier B.V. All rights reserved.