Lead(II) tetrafluoroborate and hexafluorophosphate complexes with crown ethers, mixed O/S- and O/Se-donor macrocycles and unusual [BF(4)](-) and [PF(6)](-) coordination.
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.
School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK.
Paolo
P
Farina
Thomas
T
Latter
William
W
Levason
Gillian
G
Reid