Synthesis and Structure of Nickel-Containing Cuboidal Clusters Derived from [W<sub>3</sub>Se<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>]<sup>4+</sup>. Site-Differentiated Substitution at the Nickel Site in the Series [W<sub>3</sub>NiQ<sub>4</sub>(H<sub>2</sub>O)<sub>10</sub>]<sup>4+</sup> (Q = S, Se) Hernández-MolinaRita SokolovMaxim N. ClausenMaria CleggWilliam 2006 New Ni-containing heterometallic cuboidal cluster aqua complex [W<sub>3</sub>(NiCl)Se<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>]<sup>3+</sup>, the missing link in the family of the M<sub>3</sub>NiQ<sub>4</sub> clusters (M = Mo, W; Q = S, Se), has been prepared by the reaction of [W<sub>3</sub>Se<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>]<sup>4+</sup> with Ni in 2 M HCl. Single crystals of edge-linked double-cuboidal cluster [{W<sub>3</sub>NiSe<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>}<sub>2</sub>](pts)<sub>8</sub>·18H<sub>2</sub>O (pts = <i>p</i>-toluenesulfonate) were grown from the solution of the aqua complex in 3 M Hpts, and their structures were determined. The Ni site in the clusters [W<sub>3</sub>(NiCl)Q<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>]<sup>3+</sup> selectively coordinates typical π-acceptor ligands such as CO, olefins, acetylenes, phosphines, arsines, or SnCl<sub>3</sub><sup>-</sup>. This allows stabilization by coordination of such elusive species as HP(OH)<sub>2</sub> and As(OH)<sub>3</sub>. The stability constants for coordination of HP(OH)<sub>2</sub>, As(OH)<sub>3</sub>, and SnCl<sub>3</sub><sup>-</sup> were determined. The Se for S substitution increases the stability by 1−2 orders of magnitude. Supramolecular adducts with cucurbit[6]uril (Cuc), [W<sub>3</sub>(Ni(HP(OH)<sub>2</sub>))Q<sub>4</sub>(H<sub>2</sub>O)<sub>9</sub>]Cl<sub>4</sub>·Cuc·11H<sub>2</sub>O and [W<sub>3</sub>(NiAs(OH)<sub>3</sub>)S<sub>4</sub>(H<sub>2</sub>O)<sub>8</sub>Cl]Cl<sub>3</sub>·Cuc·13H<sub>2</sub>O, were isolated and structurally characterized.