Studies on reactivities of molybdenum clusters - The additive reaction of SbCl3 to trimolybdenum clusters with loose coordination sites and the crystal structure of the reaction product

Abstract

The additive reaction of SbCl3 to trimolybdenum clusters with loose coordination sites, Mo3(μ3-S) (μ-S)3 [S2P (OEt)2]4 · L' (1 L' H2O; 2, L' C3H3ON), in a C2H5OH-HCl medium yields complexes {Mo3 (μ3-S) [(μ-S)3 · SbCl3] [S2P (OEt)2]4 · (C2H5OH)} (C2H5OH) (3) and {Mo3 (μ3-S) [(μ-S)3 · SbCl3] [S2P (OEt)2]3 [SXP (OEt)2] · (C3H3ON)} (X S,O) (4), respectively. The crystal and molecular structures of these two compounds have been determined by single crystal X-ray crystallography: crystal 3 belongs to the monoclinic system, P21,/n, while crystal 4 belongs to the triclinic system, P 1, The intensity data were collected on an Enraf-Nonius CAD-4 diffractometer with graphite-monochromatized MoKα radiation by using the ω-2θ technique. The structures were solved by the Patterson method as well as direct methods and refined by full matrix least-squares method. Final R values were 0.078 for crystal 3 and 0.068 for crystal 4, respectively. The result of the structure determination showed that the two molecular structures are practically formed by connecting a trimolybdenum clusters with loose coordination sites, {Mo2(μ3-S)- (μ-S)3[S2P(OEt)2]4 · L (L C2H5OH, C3H3ON), with a SbCl3 molecule through three (μ-S) atoms to form the {Mo SbS4} core of a cubane-like type. There are relatively weak coordination bonds between the Sb and the three (μ-S) atoms, while no bonding interaction between the Sb and the three Mo atoms is found. In the additive compounds the structural character of the trimolybdenum clusters with loose coordination sites has significantly been changed. In addition, 3 still has the reactivity for the loosely coordinated EtOH to be replaced by an oxazole ring to form crystal 4. However, the three (μ-S) atoms may be regarded as triple bridging S atoms each connecting two Mo atoms and a Sb atom. The information obtained serves as an evidence that the tetranuclear clusters might be formed by a [3 + 1] reaction mode.