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(micro-NtBu)}2 (1a-1d) produce binuclear gold(I) complexes of the type, [ClAu{RP(micro-NtBu)}2AuCl] (2 R=OC6H4OMe-o, 3R=OCH2CH2OMe, 4R=NEt2, 5R=NHtBu) in quantitative yield. A similar reaction between cis-{(o-MeOC6H4O)P(micro-NtBu)}2 (1a) and [AuCl(SMe2)] in a 1:1 molar ratio afforded the mono-nuclear complex [ClAu{(o-MeOC6H4O)P(micro-NtBu)}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(micro-NtBu)}2AuBr] (7), and iodo, [IAu{(o-MeOC6H4O)P(micro-NtBu)}2AuI] (8), derivatives through halogen exchange reactions. A tetranuclear gold(I) macrocycle [Au{(o-MeOC6H4O)P(micro-NtBu)}2]4(ClO4)4 (9) and a mononuclear gold(I) complex [Au({(o-MeOC6H4O)P(micro-NtBu)}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 AuI macrocycle 9 reveals the encapsulation of one ClO4- anion inside the bowl shaped macrocyclic cavity through weak Au...O and C-H...O interactions.