title: Preparation, structure, and properties of the corner-shared double cubes [Mo(6)HgQ(8)(H(2)O)(18)](8+) (Q = S, Se) and tungsten analogues.
abstract: The purple corner-shared double cube [Mo(6)HgS(8)(H(2)O)(18)](8+) derivative of green [Mo(3)S(4)(H(2)O)(9)](4+), obtained under air-free conditions by the reaction with Hg(0) (metal), is also formed with Hg(I)(2). The Hg(I)(2) reaction is accounted for by the disproportionation Hg(I)(2) <==> Hg(0) + Hg(II), which is a source of Hg(0). X-ray crystallographic information on the blue partially Cl(-) substituted cucurbituril supramolecular assemblies [Mo(6)HgQ(8)Cl(4)(H(2)O)(14)](C(36)H(36)N(24)O(12))Cl(4).14H(2)O (1) and of the Se analogue [Mo(6)HgSe(8)Cl(4) (H(2)O)(14)](C(36)H(36)N(24)O(12))Cl(4).14H(2)O (2) have been determined. The product [W(6)HgSe(8)Cl(4)(H(2)O)(14)](C(36)H(36)N(24) O(12)) Cl(4).14H(2)O (3) has also been obtained, but there is no evidence for [W(6)HgS(8)(H(2)O)(18)](8+) and related forms. The formation of [Mo(6)HgS(8)(H(2)O)(18)](8+) by the reaction of [Mo(3)S(4) (H(2)O)(9)](4+) with Hg(0) under anaerobic conditions maximizes after approximately 40 h in 2.0 M HCl, but requires longer reaction time ( approximately 120 h) in 2.0 M Hpts (p-toluenesulfonic acid) and in 2 M HClO(4) ( approximately 6 days). In 2.0 M HCl there is little absorbance increase until [Mo(3)S(4)(H(2)O)(9)](4+) exceeds 1.2 x 10(-)(3) M, which is explained by a dependence of the formation K (265 M(-1)) on [Mo(3)S(4)(H(2)O)(9)(4+)](2). Furthermore, on dilution of column-purified [Mo(6)HgS(8)(H(2)O)(18)](8+), Beer's law is not obeyed and equilibria involving 2[Mo(3)S(4)(H(2)O)(9)](4+) are apparent. The kinetics of formation of [Mo(6)HgS(8)(H(2)O)(18)](8+) is first-order in [Mo(3)S(4)(H(2)O)(9)](4+), consistent with rate-determining formation of the single cube [Mo(3)HgS(4)(H(2)O)(x)](4+). The oxidations of [Mo(6)HgS(8)(H(2)O)(18)](8+) with [Fe(H(2)O)(6)](3+) and [Co(dipic)(2)](-) are complicated by the release of [Hg(H(2)O)(6)](2+), which also functions as an oxidant. Similar results are obtained for [Mo(6)HgSe(8)(H(2)O)(18)](8+) and the less extensively studied [W(6)HgSe(8)(H(2)O)(18)](8+).
authors.affiliation: Department of Chemistry, The University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: V P
authors.initials: VP
authors.lastname: Fedin
authors.forename: M
authors.initials: M
authors.lastname: Sokolov
authors.forename: G J
authors.initials: GJ
authors.lastname: Lamprecht
authors.forename: R
authors.initials: R
authors.lastname: Hernandez-Molina
authors.forename: M S
authors.initials: MS
authors.lastname: Seo
authors.forename: A V
authors.initials: AV
authors.lastname: Virovets
authors.forename: W
authors.initials: W
authors.lastname: Clegg
authors.forename: A G
authors.initials: AG
authors.lastname: Sykes