Binary transition metal dinitrogen complexes. I. Matrix infrared and Raman spectra, structure and bonding of Ni(N2)n and Pd(N2)m(n = 1-4 and m = 1-3)

Abstract

The products of the cocondensation reactions of Ni and Pd atoms with N2 at 4.2-10'K are investigated by matrix isolation infrared and Raman spectroscopy and are shown to be binary dinitrogen complexes of the form of Ni(N2), and Pd(N2)m. Examination of the reaction products in pure 14N2,in 14N2/15N2, in dilute Ar/14N2, Ar/14N2/15N2 and Ar/14N5N matrices establishes the stoichiometries of the complexes to be respectively n = 1-4 and m = 1-3. Structural assignments can be made for most of the complexes on the basis of infrared and Raman activities and are found to be similar to the analogous carbonyls. Isotopic frequencies and integrated infrared absorption intensities, computed for the NN stretching modes of the individual dinitrogen complexes on the basis of the Cotton-Kraihanzel force field approximation and on isotopic intensity sum rules, are found to be in close agreement with the observed values. Ni(N2)4 in argon is a regular tetrahedral molecule with “end on bonded” dinitrogen. In nitrogen, however, it is slightly distorted. Calculations show that a substitutional site symmetry C2 for Ni(N2) satisfactorily accounts for all of the spectral lines observed for the complex in nitrogen.