The addition reaction of SbCl3 to Mo3(m3-S)(m-S)3[S2P(OEt)2]4L (L = H2O, oxazole (Q)) in a EtOH/EtOH-HCl medium yields {Mo3(m3-S)[(m-S)3SbCl3][S2P(OEt)2]4(EtOH)}(EtOH) (I) and {Mo3(m3-S)[(m-S)3SbCl3][S2P(OEt)2]3[SXP(OEt)2]Q} (X = S, O) (II) resp. I belongs to the monoclinic system, P21/n, with a 13.250(3), b 17.296(4), c 23.223(9) ? b 92.41(3)? Z = 4, R = 0.078. II belongs to the triclinic system, P1, with a 10.342(3), b 11.994(3), c 21.352(4) ? a 76.27(2), b 88.55(2), g 73.26(2)? Z = 2, R = 0.068. The 2 mol. structures are practically formed by connecting a Mo3 cluster with loose coordination sites, {Mo3(m3-S)(m-S)3[S2P(OEt)2]4L} with a SbCl3 mol. through 3 m-S atoms to form the {Mo3SbS4} core of a cubane-like type. There are relatively weak coordination bonds between the Sb and the 3 m-S atoms while no bonding interaction between the Sb and the 3 Mo atoms is found. In the addition compounds the structural character of the Mo3 clusters with loose coordination sites has not significantly changed. I crystals still have the reactivity for the loosely coordinated EtOH to be replaced by an oxazole ring to form II crystals. However, as a result of the addition, the 3 m-S atoms may be regarded as triple bridging S atoms each connecting 2 Mo atoms and a Sb atom. The information obtained in the structural anal. serves as evidence that the tetranuclear clusters might be formed by a [3 + 1] reaction mode.

Key words: CRYSTAL STRUCTURE DETERMINATION, CHLORIDE, X-RAY DIFFRACTION ANALYSIS, MOLYBDENUM COMPLEX, CLUSTER COMPOUND, ADDITION REACTION, POLYNUCLEAR COMPLEX, CONFIGURATION, ANTIMONY COMPOUNDS