The reaction of Pb[BF(4)](2) in H(2)O/MeCN solution with the macrocycle 18-crown-6 gave the dinuclear complex [{Pb(18-crown-6)(H(2)O)(μ(2)-BF(4))}(2)][BF(4)](2), containing two nine-coordinate lead centres, each bound to all six oxygens of a crown ligand, one water molecule and bridged by two μ(2)-BF(4) groups. In contrast, the oxa-thia crown [18]aneO(4)S(2) gave the mononuclear [Pb([18]aneO(4)S(2))(H(2)O)(2)(BF(4))][BF(4)] in which the lead is coordinated O(4)S(2) within the puckered ring of the macrocycle, and with two water molecules on one side of the plane and a chelating (κ(2)) BF(4)(-) on the other. The [Pb([18]aneO(4)Se(2))(BF(4))2] has the two BF(4)(-) groups arranged mutually cis and with the macrocycle folded; within each BF(4)(-) group the Pb-F distances differ by ~0.5 Å, producing a very unsymmetrical chelate. The 15-membered ring macrocycles 15-crown-5 and [15]aneO(3)S(2) produce sandwich complexes [Pb(macrocycle)(2)][BF(4)](2) which contain 10-coordinate lead centres. Pb[PF(6)](2) in H(2)O/MeCN solution formed [Pb(18-crown-6)(H(2)O)(2)(PF(6))][PF(6)] and [Pb([18]aneO(4)S(2))(H(2)O)(2)(PF(6))][PF(6)] which contain weak κ(2)-coordination of the PF(6)(-) group on the opposite side of the macrocyclic ring to two coordinated water molecules, giving 10-coordinate lead. In contrast, [Pb([18]aneO(4)Se(2))(PF(6))(2)] has two κ(2)-coordinated PF(6)(-) groups disposed cis, with a very folded macrocycle conformation. In [Pb(18-crown-6)(NO(3))(PF(6))] a chelating nitrate group occupies the coordination sites at Pb(II) instead of the two water molecules, and the weakly coordinating PF(6)(-) group is tridentate. The crystal structures of the lead nitrate complexes, [Pb(15-crown-5)(NO(3))(2)] and [Pb([18]aneO(4)Se(2))(NO(3))(2)], containing nine- and 10-coordinate lead respectively, are also reported. In solution the complexes are labile, and both conductivity and (19)F NMR spectroscopic studies show the BF(4)(-) and PF(6)(-) groups are dissociated, whereas in the nitrate complexes the anion coordination is retained in solution. The identification of the coordination modes of the NO(3)(-) and BF(4)(-) groups in the solid complexes by IR spectroscopy is discussed.

A highly unusual series of Group 2 complexes with soft thio- and selenoether coordination, [MI(2)([18]aneO(4)E(2))] (M = Ca or Sr; E = S or Se), [CaI(2)([18]aneO(2)S(4))] and [MI(2)([15]aneO(3)S(2))], has been prepared by reaction of anhydrous MI(2) with the macrocycle in dry MeCN solution. The complexes have been characterised via(1)H NMR and IR spectroscopy, microanalysis and crystallographic studies which provide unambiguous confirmation of the M-S/Se coordination. The neutral complexes are seven- or eight-coordinate with the iodo ligands cis. The long M-E bond distances of ∼3.0 Å indicate weak interactions, but they are significantly less than the sum of the van der Waals radii for M and E, and are important in facilitating isolation of the complexes. Trace hydrolysis of [MI(2)([18]aneO(4)E(2))] and [SrI(2)([15]aneO(3)S(2))] leads, unexpectedly, to displacement of the iodo ligands rather than the S/Se donor functions, and the resulting dicationic [Ca(H(2)O)(2)([18]aneO(4)S(2))]I(2), [Sr(H(2)O)(3)([18]aneO(4)S(2))]I(2)·H(2)O, [Sr(H(2)O)(3)([18]aneO(4)Se(2))]I(2) and [Sr(H(2)O)(3)([15]aneO(3)S(2))]I(2) complexes have been structurally characterised, forming eight- and nine-coordinate cations, with all the macrocyclic donor atoms coordinated. Reaction of Ca(CF(3)SO(3))(2) with [18]aneO(4)S(2) in anhydrous MeCN solution similarly affords [Ca(CF(3)SO(3))(2)([18]aneO(4)S(2))], albeit in low yield, also proven crystallographically. Using the MI(2) precursors provides a general entry into this area of coordination chemistry of these Group 2 ions, owing in part at least to their higher solubility in the weak donor (weakly competing) MeCN solvent. While CaCl(2) reacts with 18-crown-6 either directly in MeCN giving [CaCl(2)(18-crown-6)], or in the presence of SbCl(5) (to form trans-[Ca(MeCN)(2)(18-crown-6)][SbCl(6)](2)), neither of these routes works with the oxa-thia or oxa-selena crowns.

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.

No abstract

The reactions of Sn(BF4)2 and Sn(PF6)2 with crown ethers and oxa-thia- or oxa-selena-macrocycles are complex, with examples of fragmentation of the fluoroanions, and cleavage of the ligands observed, in addition to adduct formation. The reaction of Sn(BF4)2 with 15-crown-5 or 18-crown-6 produced the sandwich complex [Sn(15-crown-5)2][BF4]2 with 10-coordinate tin, and [Sn(18-crown-6)(H2O)][BF4]2·2H2O which has an hexagonal pyramidal tin centre with two long contacts to lattice water molecules (overall 7 + 2 coordination). [Sn(18-crown-6)(PF6)][PF6] is formed from 18-crown-6 and Sn(PF6)2, but the hexafluorophosphate ions hydrolyse readily in these systems to produce F(-) which coordinates to the tin to produce [Sn(18-crown-6)F][PF6], which can also be made directly from Sn(PF6)2, 18-crown-6 and KF in MeCN. The structure contains a hexagonal pyramidal coordinated Sn(II) cation with an apical fluoride. The oxa-thia macrocycle [18]aneO4S2 forms [Sn([18]aneO4S2)(H2O)2(PF6)][PF6], from which some crystals of composition [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] were obtained. The cation contains an approximately planar O4S2 coordinated macrocycle, with two coordinated water molecules on one side of the plane and a weakly bound (κ(2)) PF6(-) group on the opposite face, and with the fluoride ion hydrogen bonded to the coordinated water molecules. In contrast, the oxa-selena macrocycle, [18]aneO4Se2, produces an anhydrous complex [Sn([18]aneO4Se2)(PF6)2] which probably contains coordinated anions, although it decomposes quite rapidly in solution, depositing elemental Se, and hence crystals for an X-ray study were not obtained. Reacting Sn(BF4)2 and [18]aneO4Se2 or [18]aneO4S2 also causes rapid decomposition, but from the latter reaction crystals of the 1,2-ethanediol complex [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2 were isolated. The structure reveals the coordinated macrocycle and a chelating diol, with the O-H protons of the latter hydrogen bonded to the [BF4](-) anions. This is a very rare, structurally authenticated example of ring opening/cleavage of an oxa-thia macrocycle. The new complexes were characterised by microanalysis, IR, (1)H, (19)F{(1)H} and (31)P{(1)H} NMR spectroscopy as appropriate, and X-ray structures are reported for [Sn(15-crown-5)2][BF4]3[H3O]·H2O, [Sn(18-crown-6)(H2O)][BF4]2·2H2O, [Sn(18-crown-6)F][PF6], [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] and [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2. The complexes are compared and contrasted with chloro-tin(II) complexes of crown ethers, germanium(II) and lead(II) analogues.