Structure and bonding in the aluminum radical species Al x NH(3), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2) studied by means of matrix IR spectroscopy and quantum chemical calculations

Experimental matrix IR spectra in alliance with extensive quantum chemical calculations provide a framework for the detailed evaluation of the structures and electronic properties of the doublet species Al x NH(3), Al(NH(3))(2), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2). These species were the products of the reaction of Al atoms with NH(3) in an Ar matrix. While the two species Al x NH(3) and HAlNH(2) were already sighted in previous experiments, the results described herein lead to the first identification and characterization of HAlNH(2) x NH(3) and Al(NH(2))(2), the products of the reaction of Al atoms with two NH(3) molecules. The results allow a detailed reaction scheme leading to all the product species to be established. The unpaired electron in each of the species Al x NH(3), Al(NH(3))(2), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2) is located near the Al atom, but there is a significant degree of delocalization, especially in Al(NH(2))(2), due to pi bonding interactions. The consequences for the barrier to pyramidalization at the N-atom are discussed.