Interaction of silver(I) ions with N,N,N’,N’-tetrakis- (2-hydroxypropyl)-ethylenediamine (Quadrol)

N,N,N’,N’-tetrakis-(2-hydroxypropyl)-ethylenediamine (Sche me 1), which is also known as Quadrol (Q), due to its perfect chelating properties with regard to copper(II) ions is widely used as a ligand in electroless copper plating solutions [1–6]. Therefore, analysis of literature sources on the interaction of metal ions with Quadrol shows that the majority of publications deal with copper(II). Spectrophotometric, conductometric and pH-metric titration methods were applied for investigation of Cu(II)-Q complex formation, showing that Quadrol forms a complex with Cu(II) ions in the molar ratio 1 : 1, the stability constant logarithm (logβ1) being approximately 9 [7]. The complex of the same composition with the logβ1 = 8.45 was identified when the pH-metric titration method was used [8]. The authors of Ref. [9] detected the presence of a diligand complex of CuQ2 2+ (logβ2 = 13.6) besides CuQ 2+ (logβ1 = 9.8), and have investigated the crystal and molecular structure of the latter complex [10]. The presumption of the existence of more stable copper(II)-Quadrol complexes was stated in [11], and a detailed polarographic investigation of Cu(II) complex formation with Quadrol was carried out in a wide pH range. The authors observed formation of the above-mentioned complexes of CuQ2+ and CuQ2 2+ (logβ1 = 10.6 and logβ2 = 14.6) within the pH range from 6 to 8, whereas a sharp increase in Cu(II) complexation was observed at pH over 10, showing formation of Cu(II)–Quadrol hydroxycomplexes CuQ(OH)2 and CuQ2(OH)2. According to the authors, the determined complex compounds are among the most stable Cu(II) complexes under these conditions (logβCuQ(OH)2 = 26.9 ± 0.5 and logβCuQ2(OH)2= = 29.1 ± 0.3. The pCu values are much higher than 20 at pH over 10, and this enables the existence of rather concentrated alkaline Cu(II) solutions in the presence of Quadrol [11]. Therefore, the use of Quadrol in electroless copper plating solutions is quite natural. The better technological parameters of these solutions compared with other commonly used