Molecular orbital study on the reaction process of dimethylamine borane as a reductant for electroless deposition

The oxidation mechanism of dimethylamine borane (DMAB), which acts as a reductant in the electroless deposition process, was studied using ab initio molecular orbital approaches such as Hartree-Fock (HF) and second order Møller-Plesset (MP2) calculations. The overall oxidation process of the DMAB was divided into each elementary reaction in which OH^- substitutes H one by one and eventually forms B(OH)₄ ^-. The oxidation mechanism of DMAB in the isolated state, which was previously proposed by us, was refined using more accurate basis sets, and the effects of solvation and interaction with metal surface sites on the oxidation mechanism were also studied. Taking the solvation effect into consideration using the self-consistent reaction field method with an isodensity polarized continuum model (SCRF-IPCM), the heat of oxidation was transferred to an exothermic reaction with decreasing dielectric constant. This indicated that the reaction preferably proceeds at the solid|liquid interface. Combined with Cu(111) and Pd(111) neutral cluster models as metal surface sites, it was found that the oxidation reaction proceeds preferentially at the metal surface sites. It was also suggested that the catalytic activity of the deposited metal is caused by its electron acceptivity.