Infra-red spectroscopic evidence of an interaction between the NH bonds of coordinated amines and the non-bonding d-electrons of metal atoms

• Published in: Journal of inorganic & nuclear chemistry Vol. 8; pp. 67 - 74
• Main Authors: Chatt, Joseph, Duncanson, Leonard A., Venanzi, Luigi M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1958
• ISSN: 0022-1902; 1878-1225
• DOI: 10.1016/0022-1902(58)80165-7

Recent studies of the NH stretching bands of complexes trans-[ L, amM Cl 2] ( L = uncharged ligand; am = amine; M = Pt or Pd) have provided further data which can be explained by the postulated interaction between the NH groups of coordinated amines and the d-orbitals of M. These results show that the interaction is between the hydrogen atoms of the NH groups and filled orbitals of the metal atom and is not hyperconjugation. The evidence of the interaction can be classified in the following ways. 1. (i) anomalies in the relationship between the NH band frequencies and intensities due to varying amounts of double bonding between L and M. 2. (ii) conformational effects upon the hydrogen bonding properties of the complexes, e.g., primary amine complexes show a strong tendency to associate through intermolecular hydrogen bonds ( N − H … Cl) whereas secondary amine complexes in general do not. 3. (iii) o-substituted aniline complexes show more than the expected number of NH stretching bands, this being due to an equilibrium in solution between conformations of these complexes in which the interaction occurs to different extents.