Selective Formation of Gold(I) Bis-Phospholane Macrocycles, Polymeric Chains, and Nanotubes

A series
of highly flexible bis-phospholane ligands 3a–g with 5–11 methylene groups in the backbone
was synthesized and fully characterized by mass spectrometry and NMR
(1H, 13C, 31P) and IR spectroscopy.
Gold bis-phospholane macrocycles containing 16 ([Au2Cl2(μ-3a)2], 4), 20
([Au2Cl2(μ-3c)2], 5), 24 ([Au2Cl­(μ-3e)2]­Cl, 6), and 28 ([Au2Cl2(μ-3g)2], 7) atoms
in the ring were obtained in one step from [AuCl­(tht)] (tht = tetrahydrothiophene)
and 3a,c,e,g in
excellent yield. In addition, three polymers resulting from aurophilic
interactions, i.e., zigzag chains in [Au2Cl2(μ-3b)]x (8) and nanotubes in [Au2Cl2(μ-3d)]x (9) and [Au2Cl2(μ-3f)]x (10), with Au···Au distances of 309.41(2),
330.24(6), and 335.82(3) pm, respectively, were obtained. Halide abstraction
of 4–7 with AgBF4 led
to macrocycles [Au2(μ-3a)2]­(BF4)2 (11), [Au2(μ-3c)2]­(BF4)2 (12), [Au2(μ-3e)2]­(BF4)2 (13), and [Au2(μ-3g)2]­(BF4)2 (14). In 12, the monomers are connected by strong aurophilic
interactions (Au···Au 296.57(1) pm) in the solid state
with formation of a polymeric chain. All complexes were fully characterized
by NMR (1H, 13C, 31P) and IR spectroscopy,
mass spectrometry, and X-ray diffraction.