CRYSTAL-STRUCTURES OF LEAD(II) COMPLEXES WITH ANIONS OF IMINODIACETIC, HYDROXYETHYLIMINODIACETIC, NITRILOTRIACETIC, HEXAMETHYLENE-1,6-DIAMINETETRAACETIC, AND DIETHYLENETRIAMINEPENTAACETIC ACIDS

The syntheses and the X-ray structure analysis of Pb(HIda)(2). H2O (I) , [Pb(Heida)H2O](n) (II), Pb(HNta) (III), Na[Pb(Nta)] (IV), K[Pb(Nta)] (V), Ca[Pb(Nta)](2). 2H(2)O (VI), Sr[Pb(Nta)](2). 7.5H(2)O (VII), Ba[ Pb(Nta)NO3]. 1.5H(2)O (VIII), Pb-2(H(2)Hmdta)(NO3)(2). 6H(2)O (IX), an d [Pb(H(3)Dtpa)]. 2H(2)O (X) (where H(2)Ida is iminodiacetic acid, H(2 )Heida is hydroxyethyliminodiacetic acid, H(3)Nta is nitrilotriacetic acid, H(4)Hmdta is hexamethylene-1,6-diaminetetraacetic acid, and H(5) Dtpa is diethylenetriaminepentaacetic acid) are carried out. Compounds I, V-VII, and X contain two symmetry-independent lead atoms. Compound s I-IX have polymeric structures (layers in I, II, V, VI, and IX; fram eworks in III and IV; and chains in VII and VIII); X is built of discr ete complexes. Four acid complexes I, III, IX, and X exhibit different protonation modes: the first three complexes contain betaine nitrogen atoms, and, in the last complex, three acetate arms are protonated, a nd their carbonyl oxygens are coordinated by lead atoms. In IX, quater nization of the nitrogen atoms and coordination of the lead atom by tw o acetate arms attached to the same nitrogen result in the formation o f the eight-membered PbOCCNCCO ring. In complex IV, the lead atom has a coordination number of 7 and the coordination polyhedron in the form of a monocapped octahedron [the Pb-O(N) bond lengths are 2.55-2.67 An gstrom]. For the other compounds, coordination numbers and polyhedra o f lead atoms are ambiguous, because these atoms exhibit the partial st ereochemical activities of their electron pairs. In the 2.32-3.50 Angs trom range of Pb-O bond lengths, no distinct interrupt is observed tha t would allow unambiguous distinguishing of the first coordination sph ere of the metal atom. In compounds I, V, VI, and X, the stereochemica l activities of lone electron pairs of symmetry-independent lead atoms are different.