Thermally stable lead(ii) amidinates and guanidinates

Abstract

The reactions of lithium amidinates and guanidinates [Li(Fiso)] (Fiso = N,N′-bis(2,6-diisopropylphenyl)formamidinate), [Li(Piso)] (Piso = N,N′-bis(2,6-diisopropylphenyl)(tert-butyl)amidinate), [Li(CyG)] (CyG = N,N″-bis(2,6-diisopropylphenyl)-N′,N′-dicyclohexylguanidinate) and [Li(HDG)] (HDG = N,N″-bis(2,6-diisopropylphenyl)-N′-(2,6-diisopropylphenyl)guanidinate) with anhydrous PbCl₂ in THF afforded the amidinate complexes [Pb(Fiso)₂] 1, and [Pb(Piso)Cl]₂2, and the guanidinate complexes [Pb(CyG)Cl]₂3, and [Pb(HDG)Cl]₂4 in moderate yields. The complexes are thermally stable, 2, 3 and 4 decompose between 163–202 °C whilst 1 melts with decomposition to lead metal at 310 °C. 2, 3 and 4 are unsymmetrical dimers in the solid state but their NMR data suggested fluxional behaviour in solution. Storing the yellow crystals of [Pb(CyG)Cl]₂3 for one week in the perfluorinated crystallography oil under air resulted in oxygen incorporation into one isopropyl group of the CyG ligand giving a mixed amidinate-alkoxide dianion (CyGO) and afforded some new colourless crystals of [(CyGO)Pb]₂5 that were characterised by a X-ray single crystal structure determination.