An unusual assembled Pb(ii) meso-helicate that shows the inert pair effect

Abstract

A dinuclear Pb(ii) mesocate has been prepared with an unprecedented four-coordinated kernel in which the Pb(ii) lone pair is stereochemically active. This is the first time that this effect has been observed in a supramolecular Pb(ii) helicate or meso-helicate.

AgI and PbII as Additional Assembling Cations in Uranyl Coordination Polymers and Frameworks

“…The occurrence of argentophilic interactions may result in peculiar arrangements of the counterions, columnar for example, that themselves may induce novel architectures of the anionic uranyl-containing polymer . Another metallic cation displaying irregular coordination geometries and highly variable coordination numbers, ranging from 2 to 10, is lead­(II), which has not often been used in association with uranyl cations. ,,, The possible but controversial effects of the lead­(II) lone pair on its coordination preferences − adds further interest to such a study. The reported uranyl–silver­(I) complexes with carboxylate ligands involve acetate, pimelate, benzene-1,4-dicarboxylate, 1,3,5-benzenetriacetate, 1,4-naphthalenedicarboxylate, isonicotinate, 2,6-pyridinedicarboxylate, tetrahydrofurantetracarboxylate, and 2,5-thiophenedicarboxylate, while known uranyl–lead­(II) species contain acetate, 2,6-pyridinedicarboxylate, 1,3,5-benzenetriacetate, and tetrahydrofurantetracarboxylate, these four ligands being thus represented in both series.…”

Selective Metal-Assisted Assembly of Mesocates or Helicates with Tristhiosemicarbazone Ligands

“…In 2016, we published the first case of a helicate/mesocate showing the inert pair effect: a Pb­(II) hydrazone mesocate with a low coordination number . A detailed study of this mesocate indicated that the lead lone pair may prevent the ligands from crossing and therefore prevents the formation of a metallohelicate.…”

“…In 2016, we published the first case of a helicate/mesocate showing the inert pair effect: a Pb(II) hydrazone mesocate with a low coordination number. 29 A detailed study of this mesocate indicated that the lead lone pair may prevent the ligands from crossing and therefore prevents the formation of a metallohelicate. For that reason, we believe that the stereochemically active Pb(II) lone pair must be considered as an important factor that determines the assembly of Pb(II) mesocates versus helicates.…”

Metal ion complexes of nucleoside phosphorothioates reflecting the ambivalent properties of lead(ii)

“…4) where Pb 2+ shows no thiophilicity at all. Pb 2+ The reason for the unexpected property indicated above, relating to different S sites, is most likely the 6s 2 lone pair 13,86,87 of Pb 2+ which may give rise to a hemidirected structure as observed, e.g., for the complex Pb2(L)2, where L is the dianion of bis-salicyloylhydrazone and where Pb(II) is coordinated by two N and two negatively charged O sites, 88 with the result that the vacant part (cf. also Ref.…”

“…86) of the coordination sphere of Pb 2+ is occupied by the lone pair. 88 Clearly, the stereochemically active 6s 2 lone pair cannot remain in a s-orbital if it is to produce an asymmetric coordination sphere. 89 Depending on whether the 6s 2 lone pair causes a spherical or a non-spherical charge distribution around Pb(II), the geometry of the complexes is symmetric or distorted.…”