Lead(ii) tetrafluoroborate and hexafluorophosphate complexes with crown ethers, mixed O/S- and O/Se-donor macrocycles and unusual [BF4]− and [PF6]− coordination

Abstract

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.

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

“…A τ 8 value of 0 would correspond to an ideal square antiprismatic geometry and a τ 8 value of 1 would correspond to an ideal dodecahedral geometry, with intermediate values indicating the degree of distortion away from the two ideals. For the [18]aneO 2 S 4 complex the τ 8 parameter is calculated to be 0.29 and for the [18]aneO 4 Se 2 complex the τ 8 parameter is 0.93. This indicates that the latter complex is very close to an ideal dodecahedral geometry, whereas the former is better described as square antiprismatic, but with a high degree of distortion ( Fig.…”

“…Positional disorder was also present in the macrocycle ligands and was modelled similarly. The dataset for [Ca( [18]aneO 4 S 2 )(bipy)][BAr F ] 2 was collected from a poor-quality crystal which was very weakly diffracting at high angles, thus leading to very high R int values. Repeated attempts at recrystallization of the sample failed to afford better quality crystals.…”

“…6 Despite these recent developments, the synthesis of complexes of these elements retains significant challenges, not least the lability of the metal centres, which often results in unpredicted products or mixtures, even in apparently simple systems. 7 We have recently been exploring the use of weakly coordinating fluorinated tetraarylborate anions, such as [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] − (hereafter BAr F ) to obtain unusual complexes of the Group 1 metal ions, including the synthesis of homoleptic neutral diphosphine complexes of lithium and sodium, [M(L-L) 3 ][BAr F ] (M = Li or Na; L-L = Me 2 PCH 2 CH 2 PMe 2 or o-C 6 H 4 (PMe 2 ) 2 ), 8 the homoleptic octathioether complex of sodium, [Na( [24]aneS 8 )][BAr F ] ( [24]aneS 8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane), 9 complexes of Li-Cs of N 3 -, N 4 -and N 6 -donor azamacrocycles, 10 and with the heterocrowns, [18]aneO 2 S 4 (1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane), [18]aneO 4 S 2 (1,4,10,13-tetraoxa-7,16dithiacyclooctadecane) and [18]aneO 4 Se 2 (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane). 11 These contain rare coordination of the neutral sulfur or selenium donors to the alkali metal centre.…”

“…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…”

Three different structural lead(II) polymers constructed from newly designed chlorophenyl-imidazole dicarboxylate ligands

“…In contrast, relatively less attention has been paid to main group metals [9,10]. Pb(II) as a heavy p-block metal ion provides opportunity to construct novel topologies and interesting properties owing to its large radius (covalent radius being 1.46 Å) [11][12][13], flexible stereochemical activity, and sensitive coordination environment. Compared with transition or lanthanide metals, few cases of Pb (II) CPs have been reported [14,15].…”