The interaction of lead(II) with oxa-aza macrocycles: the X-ray crystal structures of lead(II) complexes of an N3O3 Schiff-base macrocycle and of the corresponding saturated macrocycle

Abstract

The complexes [PbL1(N03),]-H20, (1)-H,O, and [PbL2(N0,),]-H20, (2)-H,O, where L1 and L2 are corresponding di-imino-and diamino-macrocycles containing an N303 donor set, have been synthesized and characterised. X-Ray structural analyses of the anhydrous form of (1) and ( 2) have revealed significantly different co-ordination environments for the lead(ii) ion in the complexes. In (1 ), L1 utilises all six possible donors in a ten-co-ordinate complex, with no apparent stereochemical activity of the lone pair on lead(ii). Crystals of (1) were monoclinic, space group P2Jn (alternative no. 14) with a = 30.245( 6), b = 10.271 (2), c = 16.246(3) A, p = 95.05(3)", and

The first hemidirected nine coordinate lead(II) complex, crystal and molecular structure of [Pb(BzImH) 2 py (H 2 O) 2 (NO 3 ) 2 ] · (BzImH) 2 py · H 2 O, (BzImH) 2 py=2,6-Bis(2-benzimidazolyl)pyridine

“…The arrangement of (BzImH) 2 A compared with 2.859 A adjacent to the lone pair) supports the presence of this feature [10]. Hence, the geometry of the nearest coordination environment of every lead atom is likely caused by the geometrical constraints of coordinated (BzImH) 2 py ligand, water molecules and nitrate anions and by the influence of a stereochemically active lone pair of electrons in a hybrid orbital on the metal atom.…”

“…Details of the coordination chemistry of lead(II) compounds are frequently discussed in regard to the coordination and stereo-activity of the valence shell lone electron pairs [1][2][3][4][5][6]. The possible stereo-chemical activity of the lone pair in divalent lead compounds has recently been discussed by Shimoni-Livny et al [7] based on a thorough review of crystal data available in the Cambridge structural database (CSD).…”

“…Since the hemidirected geometry in the nine coordination lead(II) complexes is rarely observed. Possibly, presence of nine hard donor atoms (three nitrogen and six oxygen) in the coordination sphere of this complex provoke significant involvement of the 6s orbital in the valence shell and produce a gap, which forming of p-p stacking interactions between the parallel aromatic rings in the [Pb(BzImH) 2 …”

“…The crystal structure of this compound consists of monomeric units of [Pb(BzImH) 2 py(H 2 O) 2 (NO 3 ) 2 ] Á (BzImH) 2 py Á H 2 O. Each lead atom is chelated by the nitrogen atoms of (BzImH) 2 A. The coordination number in this complex is nine (three of '(BzImH) 2 py' ligand, four of nitrate anions and two of water molecules) (see Fig.…”

Two novel extended lead(II) coordination polymers generated from bridging Schiff-base ligands

“…Eight coordination modes of nitrate ion have been observed (see Chart 1): (i) terminal mono-dentate mode [23], (ii) bi-chelating mode [24], and (iii) bridging mode ðl-NO À 3 Þ including (iiia) bi-dentate chelating/bridging [25], (iiib) tri-dentate chelating/bridging [26] and (iiic) tri-dentate bi-chelating/bridging [7f,27] usually occur, while the bridging modes (iv-vi) are less commonly found. The bridging mode (iv), which the nitrate Fig.…”