[en] In complexes of lead(II) and probably in those of related species such as Ti(I) and Bi(III), the nature and form of the coordination sphere is generally determined by a number of factors, possibly including lone pair-bond pair repulsions, of comparable influence, so that seemingly minor differences in ligands or in the crystal array can have quite marked effects upon the coordination stereochemistry. Since the presence of lone pair is not directly to the central metal, the identification of these donor atoms is fundamental to the analysis of any particular system. In the present paper, we study the nature of adducts formed between lead(II) and bismuth(III) nitrate and aromatic N,N'-bidentate ligand of which 4,4'-bi thiazole. These compounds were characterized by IR, ¹H NMR, ²⁰⁷PbNMR, ¹³CNMR and CHN analysis. Their structures were determined by x-ray crystallography. Data crystallography are for [Pb(BTZ)₂(NO₃)₂: monoclinic with space group C 2/c, a=16.875(19), b=13.3895(16)(II). A^dig^, β=109.19(13)^dig^, Z=4 f.u., R was 0.0199 for N₀=2649 independent [I>2σ(I)] reflection and for [(BTZ)₂Bi(NO₃)₃: monoclinic, C 2/c, a=8.888(2)A^dig^, b=14.723(4)A^dig^, c=16.748(4)A^dig^, β=104.683(6)^dig^, V2120.1(9)a^dig³, Z=4, R₁=0.0358, wR₂= 0.0781. The coordination number for [Pb(BTZ)₂(NO₃)₂ is six and the lone pair is active. The coordination number for [Pb(BTZ)₂(NO₃)₃ is ten and the lone pair is in active. The recently studies on some of lead(II) complexes show that there is the well correlation between the chemical shift and the lone pair activity