s-Block chalcogenoether chemistry – thio- and selenoether coordination with hard Group 2 ions

Abstract

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 Group 2 dications with soft thioether- and selenoether-containing macrocycles

“…For each complex an eight-coordinate Ca 2+ centre sitting in the middle of a hexadentate macrocycle with trans MeCN ligands was observed. Similar structures have been reported for [Ca(18-crown-6)I 2 ], 27 [Ca(18-crown-6)(hmpa) 2 ] 2+ (hmpa = hexamethylphosphoramide) 26 13 contain puckered macrocycles with cis coordinated monodentate ligands. It is probable that the energy difference between the different arrangements is small and the cation geometry may be influenced by intermolecular interactions and crystal packing.…”

“…Changes in the macrocyclic coordination geometry do not significantly affect the Ca-S and Ca-Se bond lengths which are very similar between the iodide 13 and MeCN complexes, although there are some slight differences in the Ca-O bond The MeCN ligands can be displaced by neutral donors, for example 2,2′-bipyridyl, which formed [Ca( [18]aneO 4 S 2 )(bipy)]-[BAr F ] 2 . The 1 H and 13 C{ 1 H} NMR spectra contained broad resonances indicative of a dissociating system in CD 2 Cl 2 solution at ambient temperatures, but the identity was confirmed by the X-ray crystal structure (Fig.…”

“…enCIFer was used to prepare material for publication. 21 13 [Ca(MeCN) 8 ][BAr F ] 2 . A mixture of CaI 2 (0.25 g, 0.85 mmol) and Na[BAr F ] (1.50 g, 1.69 mmol) were dissolved in MeCN (10 mL) and stirred for 24 h, affording a yellow solution.…”

“…Heterocrowns containing S-or Se-donor atoms have an extensive chemistry with d-and p-block metals, 12 but examples with the s-block elements are few. In addition to the Group 13 The complex [Ca(ClO 4 ) 2 ([18]aneO 4 S 2 )], 14 the lamellar polymer [Ba{Cu(SCN) 3 ([18]-aneO 4 S 2 )}], 15 and [Mg(R-benzo [18]aneO 4 S 2 )] 16 (R-benzo [18]-aneO 4 S 2 = R-benzo-substituted [18]aneO 4 S 2 ) are also known. The present paper describes the synthesis, structures and spectroscopic properties of complexes of [18]aneO 4…”

Manganese–calcium clusters supported by calixarenes

“…As expected, the Ca⋯S distances (2.9171(8)-2.9719(8) Å) are substantially longer than the Ca⋯O distances (2.379(2)-2.478(2) Å), and are similar to those found in O 6 S 2 calcium complexes of L S 25,42 and oxa-thia crown ethers. 43 The two calixarene ligands are not co-planar, presumably due to the differing radii of the metal centres, with angle between the two S4 planes being 14.29(2)°. The resulting structure is similar to the previously reported Mn/Gd complex [Mn 2 (Gd(CH 3 OH) 2 )(μ 4 -OH)(L S ) 2 ].…”