Correlation between the M←OH2 Bond Force Constants, Energies, and Lengths and Magnetic Moments of the Metal Atoms in Isostructural Nitrilotris(methylenephosphonic) Complexes [MII(H2O)3μ-NH(CH2PO3H)3] (MII = Cr-Zn)

Abstract

The isostructural 3d transition metal complexes [M^II(H₂O)₃μ-NH(CH₂PO₃H)₃] (M^II = Cr-Zn) were studied by X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. In order to gain more in-depth knowledge about the chemical bonds in coordination compounds, correlation analysis was carried out between the force constants and energies of the M←OH₂ coordination bonds and the magnetic moments of transition metal atoms. The correlation of the force constants of the M←OH₂ bonds with the M-O(w) interatomic distances was in line with the known empirical Badger’s rule. The double linear regression between the bond energy and reciprocal of M-O(w) interatomic distances and atomic magnetic moments shows a close relationship between the M←OH₂ bond energy and the spin magnetic moment of 3d-metal atoms. The results account for the stability of Fe-containing heterometallic polymeric NTP complexes and high efficiency of NTP complexes as corrosion inhibitors for iron alloys in aqueous media.