Gold(i) complexes of cyclodiphosphazanes cis-{RP(μ-NtBu)}2: structure of a novel tetranuclear gold(i) macrocycle, [{Au{(o-MeOC6H4O)P(μ-NtBu)}2}4](ClO4)4

Abstract

Reactions of two equivalents of [AuCl(SMe₂)] with cyclodiphosphazanes cis-{RP(μ-N^tBu)}₂ (1a–1d) produce binuclear gold(I) complexes of the type, [ClAu{RP(μ-N^tBu)}₂AuCl] (2 R = OC₆H₄OMe-o, 3 R = OCH₂CH₂OMe, 4 R = NEt₂, 5 R = NH^tBu) in quantitative yield. A similar reaction between cis-{(o-MeOC₆H₄O)P(μ-N^tBu)}₂ (1a) and [AuCl(SMe₂)] in a 1 : 1 molar ratio afforded the mono-nuclear complex [ClAu{(o-MeOC₆H₄O)P(μ-N^tBu)}₂] (6). Addition of two equivalents of CuX (X = Br, I) to the chloro derivative 2 leads to the formation of bromo, [BrAu{(o-MeOC₆H₄O)P(μ-N^tBu)}₂AuBr] (7), and iodo, [IAu{(o-MeOC₆H₄O)P(μ-N^tBu)}₂AuI] (8), derivatives through halogen exchange reactions. A tetranuclear gold(I) macrocycle [Au{(o-MeOC₆H₄O)P(μ-N^tBu)}₂]₄(ClO₄)₄ (9) and a mononuclear gold(I) complex [Au({(o-MeOC₆H₄O)P(μ-N^tBu)}₂)₂]ClO₄ (10) were obtained, respectively, from 1 : 1 and 2 : 1 stoichiometric reactions between 1a and [Au(SMe₂)₂]ClO₄. Molecular structures of complexes 4, 6, 7, 8 and 9 are confirmed by single-crystal X-ray diffraction studies. Interestingly, the crystal structure of the tetra-nuclear Au^I macrocycle 9 reveals the encapsulation of one ClO₄⁻ anion inside the bowl shaped macrocyclic cavity through weak Au⋯O and C–H⋯O interactions.