Ligand Substitution Reactions of W<sub>6</sub>S<sub>8</sub>L<sub>6</sub> with Tricyclohexylphosphine (L = 4-<i>tert</i>-Butylpyridine or <i>n</i>-Butylamine):  <sup>31</sup>P NMR and Structural Studies of W<sub>6</sub>S<sub>8</sub>(PCy<sub>3</sub>)<i><sub>n</sub></i>(4-<i>tert</i>-butylpyridine)<sub>6</sub><sub>-</sub><i><sub>n</sub></i> (0 < <i>n</i> ≤ 6) Complexes

The substitution reactions by bulky tricyclohexylphosphine (PCy<sub>3</sub>) ligands on W<sub>6</sub>S<sub>8</sub>L<sub>6</sub> (L = 4-<i>tert</i>-butylpyridine or <i>n</i>-butylamine) clusters were investigated to prepare clusters with mixed axial ligands for low-dimensional cluster linking. When 4−6 equiv of PCy<sub>3</sub> are used to react with W<sub>6</sub>S<sub>8</sub>(4-<i>tert</i>-butylpyridine)<sub>6</sub> (<b>4</b>) in THF, <i>cis</i>-W<sub>6</sub>S<sub>8</sub>(PCy<sub>3</sub>)<sub>4</sub>(4-<i>tert</i>-butylpyridine)<sub>2</sub> (<b>1</b>) is preferentially formed. But when starting with W<sub>6</sub>S<sub>8</sub>(<i>n</i>-butylamine)<sub>6</sub> (<b>2</b>), only W<sub>6</sub>S<sub>8</sub>(PCy<sub>3</sub>)<sub>6</sub> (<b>3</b>) is produced with 6 equiv of PCy<sub>3</sub>. Other conditions with fewer equivalents of PCy<sub>3</sub> led to mixtures of partially substituted complexes in the W<sub>6</sub>S<sub>8</sub>L<sub>6</sub><sub>-</sub><i><sub>n</sub></i>(PCy<sub>3</sub>)<i><sub>n</sub></i> (0 ≤ <i>n</i> ≤ 6, L = 4-<i>tert</i>-butylpyridine or <i>n</i>-butylamine) series. A significantly distorted structure for <b>1</b> helps to explain its preferential formation. <sup>1</sup>H NMR spectra were collected for clusters <b>1 </b>and <b>2</b> and <sup>31</sup>P NMR spectra for <b>1</b> and W<sub>6</sub>S<sub>8</sub>(4-<i>tert</i>-butylpyridine)<sub>6</sub><sub>-</sub><i><sub>n</sub></i>(PCy<sub>3</sub>)<i><sub>n</sub></i> complexes. P−P coupling through P−W−W−P is reported for the first time in octahedral metal clusters and shown to be very useful in identifying nearly all the W<sub>6</sub>S<sub>8</sub>L<sub>6</sub><sub>-</sub><i><sub>n</sub></i>(PR<sub>3</sub>)<i><sub>n</sub></i> complexes and their stereoisomers in the mixtures even before individual species are isolated.