INTRAMOLECULARLY HYPERCOORDINATED ORGANOLEAD COMPOUNDS: (o-MeOC6H4-CH2)PbPh2R, R = Ph, Cl, WITH Pb–O SECONDARY BONDING

The tetrahedral geometry of organolead(IV) compounds can be readily transformed by using an organic ligand containing a dangling-arm oxygen functionality. The acidity of the Pb center results in so-called secondary bonding between O and Pb thereby pushing the geometry at Pb toward a trigonal bipyramidal (tbp) structure. Replacing a phenyl group by a chlorine atom dramatically enhances this phenomenon. Thus for (o-methoxybenzyl) triphenyllead (4), and (o-methoxybenzyl)diphenyllead chloride (5), the Pb–O internuclear distances are 3.362(4) and 2.845(3) Å, respectively; 83% (4) and 70% (5) of the sum of the van der Waals Pb and O radii. Within the group 14 element congeners the structural analysis of the (o-methoxybenzyl)triphenylE compounds, E = Si, Ge, Sn, and now Pb, demonstrates the relative acidities of E are Si < Ge < Sn < Pb.

Between MOFs and molecules: organolead(IV) compounds with chain structures

Organolead compounds are of interest mainly as catalysts and organolead halides have proved to be very efficient materials for solar cells. Two organolead(IV) dimethylarsinates, namely catena-poly[[triphenyllead(IV)]-μ-chlorido-[triphenyllead(IV)]-μ-dimethylarsinato-κ2 O:O′], [Pb2(C6H5)6(C2H6AsO2)Cl] n or [(Ph3Pb)2Cl(O2AsMe2)], (1), and poly[chlorido(μ3-dimethylarsinato-κ3 O:O,O′:O′)diphenyllead(IV)], [Pb(C6H5)2(C2H6AsO2)Cl] n or [(Ph2ClPb)(O2AsMe2)], (2), together with the triphenyllead(IV) diphenylphosphinate catena-poly[[triphenyllead(IV)]-μ-diphenylphosphinato-κ2 O:O′], [Pb(C6H5)3(C12H10O2P)] n or [(Ph3Pb)(O2PPh2)], (3), have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy and mass spectrometry. In (1), a chain structure was found with alternating chloride and Pb—O—As—O—Pb arsinate bridges between five-coordinate PbIV atoms. In (2), bidentate and chelate-like bonded dimethylarsinate ligands form double chains with heptacoordinated PbIV atoms. In (3), a pentacoordinated PbIV atom is connected by Pb—O—P—O—Pb phosphinate bridges to form a linear chain. Obviously, the steric demand of the phenyl ligands at PbIV reduces the possibility of interconnections via polydentate ligands to one dimension only. Thus, no metal–organic frameworks (MOF) are formed but instead various chain structures are observed.