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

Binary Transition Metal Dinitrogen Complexes. Part II. Matrix Infrared and Raman Spectra, Structure, and Bonding of Pt(N2)n (where n = 1–3)

“…These binary dinitrogen complexes have, with the exception of Pt(N,),, been shown to be similar to the corresponding binary carbonyl complexes in a number of ways, some of which have been discussed previously (1). The behavior of Pt in the group deserves special attention.…”

“…The furnace used for the evaporation of the metals has been described previously (1). The rate of metal atom depositions was continuously monitored using a quartz crystal microbalance (12).…”

“…We have recently shown that the method of Bor (3) and Haas and Sheline (4), used for calculating the effect of 13C160/'2C180 isotopic substitution on the relative intensities of the infrared bands of metal carbonyls, can also be applied successfully to 14N2/15N2 isotopic substituted dinitrogen complexes of Ni and Pd (1) and that the Cotton-Kraihanzel force field approximation (2) usually applied to carbonyls is equally applicable to binary dinitrogen complexes. We therefore use an identical approach to that previously outlined for Pd(N,), where m = 0-3 to calculate the intensities and frequencies of the mixed isotopic species Pt(N,),.…”

“…molecular structures of Ni(N,), and Pd(N,), were shown to be similar to the corresponding binary carbonyls Ni(CO), and Pd(CO),. Also the Cotton-Kraihanzel force field approximation (2) and isotope intensity sum rules (3,4) applied usually to CO in carbonyls, were shown to be I equally successful for predicting the frequencies and intensities of infrared active NN stretching modes for coordinated N, in binary dinitrogen I complexes and their mixed isotopic molecules (1).…”

Binary Dinitrogen Complexes of Rhodium, Rh(N2)n (where n = 1–4), in Low Temperature Matrices

“…Recently, matrix isolation vibrational spectros- (3,4). One ofthe obvious benefits of the study of these matrix isolated species (as well as the analogous M(CO),, (5, 6) a n d M(O,),,, (7) complexes) is the ability to study the effect of increased coordination on the strengths of the ligand and metal-ligand bonds, without the necessity of including other stabilizing ligands.…”