Abstract
Complexes of the oxa-thia macrocycles [18]aneO4S2, [15]aneO3S2 and the oxa-selena macrocycle [18]aneO4Se2 (L) of types [MCl2(L)]FeCl4 (M = Sc or Y) were prepared from [ScCl3(thf)3] or [YCl2(THF)5][YCl4(THF)2] and the ligand in anhydrous MeCN, using FeCl3 as a chloride abstractor. The [MI2(L)]I, [LaI3(L)] and [LuI2(L)]I have been prepared from the ligands and the appropriate anhydrous metal triiodide in MeCN. Complexes of type [LaI3(crown)] and [LuI2(crown)]I (crown = 18-crown-6, 15-crown-5) were made for comparison. Use of the metal iodide results in complexes with high solubility compared to the corresponding chlorides, although also with increased sensitivity to moisture. All complexes were characterised by microanalysis, IR, (1)H, (45)Sc and (77)Se NMR spectroscopy as appropriate. X-ray crystal structures are reported for [ScCl2([18]aneO4S2)][FeCl4], [ScI2([18]aneO4S2)]I, [YCl2(18-crown-6)]3[Y2Cl9], [YCl2([18]aneO4S2)][FeCl4], [LaI3(15-crown-5)], [LaI2(18-crown-6)(MeCN)]I, [LuI(18-crown-6)(MeCN)2]I2, [Lu(15-crown-5)(MeCN)2(OH2)]I3, [LaI3([18]aneO4S2)], [LaI([18]aneO4S2)(OH2)]I2, [LaI3([18]aneO4Se2)] and [LuI2([18]aneO4Se2)]I. In each complex all the neutral donor atoms of the macrocycles are coordinated to the metal centre, showing very rare examples of these oxophilic metal centres coordinated to thioether groups, and the first examples of coordinated selenoether donors. In some cases MeCN or adventitious water displaces halide ligands, but not the S/Se donors from La or Lu complexes. A complex of the oxa-tellura macrocycle [18]aneO4Te2, [ScCl2([18]aneO4Te2)][FeCl4] was isolated, but is unstable in MeCN solution, depositing elemental Te. YCl3 and 18-crown-6 produced [YCl2(18-crown-6)]3[Y2Cl9], the asymmetric unit of which contains two cations with a trans-YCl2 arrangement and a third with a cis-YCl2 group.
Highlights
The coordination chemistry of the trivalent lanthanides is characterised by an affinity for small hard donor ligands – preferably charged anions such as F−, O2−, OH−, OR− or NO3−, or polydentate nitrogen or oxygen donor ligands.1 The bonding is usually described as predominantly ionic or highly polar iondipole in nature, the complexes often have high coordination numbers reflecting the large ion size and are labile in solution
The new complexes contain rare examples of these hard metal ions coordinated to neutral sulfur donor centres, and include k Poor quality crystals of [LuI2([18]aneO4S2)]I·2MeCN were isomorphous with the selena-oxo-crown analogue. a = 15.440(6), b = 11.847(4), c = 14.821(6), α = β = γ = 90, V = 2711.2(18), z = 4
All contain endo-coordinated macrocycles with all of the neutral donors bonded to the metal centres
Summary
The coordination chemistry of the trivalent lanthanides is characterised by an affinity for small hard donor ligands – preferably charged anions such as F−, O2−, OH−, OR− or NO3−, or polydentate nitrogen or oxygen donor ligands.1 The bonding is usually described as predominantly ionic or highly polar iondipole in nature, the complexes often have high coordination numbers reflecting the large ion size (ionic radii in 6-coordination La3+ 1.22 Å–Lu3+ 0.85 Å) and are labile in solution. The 45Sc NMR resonance observed at δ = 206, seems inconsistent with the presence of coordinated iodide, and it may be that the iodides are displaced in solution by MeCN which would produce a significant low frequency shift.
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