Synthesis and Structure of Two Octahedral Molybdenum Chloride Sulfide Clusters

摘要

A preparation for chloride sulfide Mo sub 6 X sub 8 clusters has been devised which employs substitution by sulfide into the Mo sub 6 Cl sub 84+ cluster. The Mo sub 6 Cl sub 7 S exp 3+ cluster has been isolated in the two compounds (C sub 5 H sub 5 NH) sub 3 ((Mo sub 6 Cl sub 7 S)Cl sub 6 ) x 3(C sub 5 H sub 5 NH)Cl and (C sub 5 H sub 5 NH) sub 3 ((Mo sub 6 Cl sub 7 S)Cl sub 6 ). The structures of both compounds were determined by single crystal x-ray techniques. Despite the different site symmetries of the (Mo sub 6 Cl sub 7 S)Cl sub 63- units in the two compounds (S sub 6 in the former, C/sub i/ in the latter), corresponding average bond distances and angles are equivalent. The infrared spectra (200 to 450 cm exp -1 ) of the two compounds are identical, and exhibit a band at 421 cm exp -1 assigned to a (Mo sub 6 Cl sub 7 S)Cl sub 63- cluster vibration of predominant Mo-S character. Resolution of the chlorine 2p photoelectron spectra into components reveals not only that sulfide occupies a bridging ligand site of the (Mo sub 6 Cl sub 7 S)Cl sub 63- cluster, but also that the difference between the chlorine 2p binding energies of the bridging and terminal chlorides is anomalously small. The Mo sub 6 S sub 6 Cl sub 2 cluster has been isolated in the novel compound (Mo sub 6 S sub 6 Cl sub 2 )(NC sub 5 H sub 5 ) sub 6 . The structure, determined by single crystal x-ray techniques, consists of an approximately cubic Mo sub 6 X sub 8 cluster with six terminal pyridine ligands. (Mo sub 6 S sub 6 Cl sub 2 )(NC sub 5 H sub 5 ) sub 6 is the first example of a Mo sub 6 X sub 8 cluster with terminal ligands which has fewer that 24 electrons in its metal-metal bonding orbitals. X-ray powder data indicates this compound may be one composition in a molecular solid solution (Mo sub 6 S/sub 7-x/Cl/sub 1+x/)(NC sub 5 H sub 5 ) sub 6 (0 less than or equal to x less than or equal to 2). (ERA citation 05:016250)