Gas-Phase Reactions between Silane and Ammonia: A Theoretical Study

Abstract

Gas-phase reactions between silane (SiH4) and ammonia (NH3) were investigated using ab initio calculations at the CCSD(T)/6-311++g**//MP2/6-31+G* level. Within the energy range of 180 kcal/mol, we located 34 equilibrium and 23 transition states on the potential energy surfaces of the Si−N−H systems. The initially weakly bonded molecular complex H3N−SiH4 eliminates the first hydrogen molecule (H2) to form the Si−N bond three ways. The first route is through a dihydrogen-bonded transition state, over a barrier of 49.31 kcal/mol, leading directly to the most stable product silylamine (H2N−SiH3). The second route is through SiH4 dissociating into SiH2 and H2, over a barrier of 57.47 kcal/mol, leading to the dative-bonded silylammonia complex H3N−SiH2. The third route is through a stepwise atomic dissociation and radical formation process, over a barrier of 131.21 kcal/mol, also leading to H3N−SiH2. With more energy, both H2N−SiH3 and H3N−SiH2 are liable to further H2 or H elimination, leading to smaller speci...