Coordination Chemistry of Calix-Phosphanes: Cooperativity in the Assembly of a Tetragold Calixarene Complex

✍ Scribed by Cedric B. Dieleman; Dominique Matt; Anthony Harriman

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 291 KB
• Volume: 2000
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/(sici)1099-0682(200005)2000:5<831::aid-ejic831>3.0.co;2-2

✦ Synopsis

Assemblage of the tetragold complex [L⋅(AuCl) 4 ] from p-tertbutyl-calix[4]-(OCH 2 PPh 2 ) 4 (L) and [AuCl(tetrahydrothiophene)] was investigated by NMR and UV/Visible spectroscopic titrations. Three steps could be resolved and are assigned, respectively, to addition of one, two and four AuCl units to the macrocyclic ligand. At each stage of metallation, symmetrical species persist on the NMR time scale since the bound AuCl fragments migrate between the different phosphorus centers via both intra-and intermolecular processes. The derived stability constants (logβ 1 = 4.4 ± 0.2, logβ 2 = 7.0 ± 0.7, and logβ 4 = 14.5 ± 2.0) indicate both positive and nega-

Results and Discussion

As pointed out in a previous study, 31 P and 1 H NMR spectroscopy suggests that addition of sub-stoichiometric amounts of [AuCl(THT)] to L in CDCl 3 forms a monogold species [11] that co-exists with the free ligand. In fact,