Selective formation of silver(i) bis-phospholane macrocycles and further evidence that gold(i) is smaller than silver(i)†
A new synthetic approach to highly flexible bis-phospholanes from 1-benzylphospholane (1) as starting material is described. Silver(I) macrocycles containing 16 ([Ag2(μ-3a)2](BF4)2, 4), 20 ([Ag2(μ-3b)2](BF4)2, 5), 24 ([Ag2(μ-3c)2](BF4)2, 6), and 28 ([Ag2(μ-3d)2](BF4)2, 7) atoms in the ring were obtained in one step from AgBF4 and the respective bis-phospholane (C4H8P)(CH2)n(PC4H8) (n = 5, 7, 9, 11; 3a–d) in excellent yields. Comparison of 6 with the previously reported isomorphous complex [Au2(μ-3c)2](BF4)2 gave further evidence that gold(I) is significantly smaller than silver(I). All complexes were fully characterized by NMR and IR spectroscopy, mass spectrometry, and X-ray diffraction.