In this paper, we report a high-yield procedure for the synthesis of isolated W6S8(4-tert-butylpyridine)6 clusters from isolated tungsten chloride clusters. We also show that the 4-tert-butylpyridine ligand can be exchanged with triethylphosphine and piperidine.

Eleven organic Lewis bases were investigated as potential ligands (L) on W(6)S(8)L'(6) clusters by exploring ligand exchange reactions to form W(6)S(8)L(6) clusters. Six new homoleptic W(6)S(8)L(6) cluster complexes were prepared and characterized with L = tri-n-butylphosphine (P(n)Bu(3)), triphenylphosphine (PPh(3)), tert-butylisocyanide ((t)BuNC), morpholine, methylamine (MeNH(2)), and tert-butylamine ((t)BuNH(2)). While partial replacement of ligands occurred with diethylamine (Et(2)NH) and dibutylamine (Bu(2)NH), homoleptic clusters could not be prepared by these exchange reactions. When aniline, tribenzylamine, and tri-tert-butylphosphine were the potential ligands, no exchange was observed. From ligand exchange studies of these ligands and others previously studied, a thermodynamic series of binding free energies for ligands on W(6)S(8)L(6) clusters was established as the following: non-Lewis base solvents, aniline, P(t)()Bu(3), etc. << Et(2)NH, Bu(2)NH < (t)BuNH(2) < morpholine, piperidine < or = (n)BuNH(2), MeNH(2) < or = 4-tert-butylpyridine, pyridine < (t)BuNC < tricyclohexylphosphine (PCy(3)) < PPh(3), P(n)Bu(3) < or = triethylphosphine (PEt(3)). Structures of the new cluster complexes were determined by X-ray crystallography. The new compounds were also characterized by NMR spectroscopy and thermogravimetric analyses (TGA). The W-L bond orders and TGA data qualitatively agree with the thermodynamic series above.

We have synthesized two compounds, W 6 S 8 [bis(diphenylphosphino)ethane] 6 (1) and W 6 S 8 (4,4′-bipyridine) 6 (2), in which ditopic ligands associate with the W 6 S 8 cluster in monotopic fashion. Compound 1 was synthesized through ligand exchange on W 6 S 8 (tbp) 6 (tbp = 4-tert-butylpyridine) in benzene and crystallized in the R3 space group with a = b = 29.7159(13) Å and c = 14.2188(9) Å. Compound 2 was synthesized by ligand exchange on W 6 S 8 (tbp) 6 in aniline and crystallized as 2c5aniline in the P1 -