Infrared spectra of transition-metal

The most important use of energy level diagrams described in 3.5 is to interpret visible to near-infrared spectra of transition metal compounds and minerals. The diagrams provide qualitative energy separations between split 3d orbitals and convey information about the number and positions of absorption bands in a crystal field spectrum. Two other properties of absorption bands alluded to in 3.3 are their intensities and widths. 

F. A. Cotton The infrared spectra of transition metal complexes, pp. 301-399 (222), with a section on metal carbonyls and cyclopentadienyls. 

The infrared spectra of transition metal carbonyl anions provide an excellent illustration of the effect on the charge of the n acceptor ability of CO as expected, the more negative the charge, the stronger the n acceptance and the lower the energy of the C-0 stretching vibrations (Table 4-2). 

There followed many other exciting adventures involving studies of the infrared spectra of transition-metal complexes, but I will mention just one which I find particularly memorable. This followed the discovery by Bernard Shaw of a remarkably stable volatile platinum complex produced by reduction of [PtCl2(PEt3)2], the spectrum of which had a very strong and sharp absorption band near 2200 cm ... 

COTTON, F.A., "The Infrared Spectra of Transition Metal Complexes" in LEWIS, J., and WILKINS, R. G., "Modern Coordination Chemistry", Inter -science, 1960 NAKAMOTO, K., "Infrared Spectra of Inorganic and Coordination Compounds", Wiley, 1963. 

Gong Y, Zhou M (2009) Infrared spectra of transition-metal dioxide anions MO - (M = Rh, Ir, Pt, Au) in solid argon. J Phys Chem Al 13 4990-4995... 

F. A. Cotton, The Infrared Spectra of Transition Metal, in Modern Coordination Chemistry Complexes (J. Lewis and R. G. Wilkins, eds.). Interscience Publishers, New York (1960). 

A general discussion of the infrared spectra of transition metal complexes has been published (23). Although correlations of CO bending modes (24) and of band intensities (25,26) have appeared and vibrations of other ligands are often noted, the number of CO stretching modes and their exact frequencies are the data most frequently cited for metal carbonyl com-... 

The most recent fairly comprehensive review Of the vibrational spectra of transition metal carbonyls is contained in the book by Braterman1. This provides a literature coverage up to the end of 1971 and so the subject of the present article is the literature from 1972 through to the end of 1975. Inevitably, some considerable selectivity has been necessary. For instance, a considerable number of largely preparative papers are not included in the present article. Tables A-E provide a general view of the work reported in the period. Table A covers spectral reports and papers for which topics related purely to vibrational analysis are not the main objective. Papers with the latter more in view are covered in Table C. Evidently, the division between the two is somewhat arbitrary. Other tables are devoted to papers primarily concerned with the spectra of crystalline samples — Table B — to reports of infrared and Raman band intensities — Table D and sundry experimental techniques or observations - Table E. Papers on matrix isolated species, which are covered elsewhere in this volume, are excluded. 

Evaluation of A Energy separations between resolved 3d orbital energy levels correspond to visible and near-infrared radiation. Measurements of absorption spectra of transition metal compounds and minerals are used to obtain A and to evaluate the CFSE of the ions. Crystal field splittings may also be estimated from plots of thermodynamic data for the first-series transition metal compounds. The magnitude of A depends on ... 

Chapter 5 summarizes the crystal field spectra of transition metal ions in common rock-forming minerals and important structure-types that may occur in the Earth s interior. Peak positions and crystal field parameters for the cations in several mineral groups are tabulated. The spectra of ferromagnesian silicates are described in detail and correlated with the symmetries and distortions of the Fe2+ coordination environments in the crystal structures. Estimates are made of the CFSE s provided by each coordination site accommodating the Fe2+ ions. Crystal field splitting parameters and stabilization energies for each of the transition metal ions, which are derived from visible to near-infrared spectra of oxides and silicates, are also tabulated. The CFSE data are used in later chapters to explain the crystal chemistry, thermodynamic properties and geochemical distributions of the first-series transition elements. 

Cj B, Drake AF, Kuroda R et al (1980) Vibrational electronic interaction in the infrared circular-dichroism spectra of transition-metal complexes. Chem Phys Lett 70 8-10... 

Infrared and Raman spectral studies of 77-complexes formed between metals and C H rings Vibrational spectra of transition metal carbonyl complexes... 

The infrared spectra of several metallic nitrates were examined [ ] and the observation was made that in going from a monovalent metallic nitrate to a tetravalent metallic nitrate there is an increased lowering of the nitrate symmetry, and a transition from a point group Dsk symmetry to a point group C2V symmetry. 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Infrared spectra have been recorded for the parent tetrazole (ttaH), its sodium salt, and a range of transition metal derivatives (94). In subsequent work the infrared spectra of sodium tetrazolate and of the copper complex Cu(tta)2 H20 were assigned and a vibrational analysis was reported for the tetrazolate anion (77). Infrared data have been... 

R. Fournier and I. Papai, in Recent Advances in Density Functional Methods, Part I, D. P. Chong, Ed., World Scientific, Singapore, 1995, pp. 219-285. Infrared Spectra and Binding Energies of Transition Metal-Monoligand Complexes. 

The inverse fifth-power dependency of crystal field splitting on metal-oxygen distance expressed in eq. (2.17) is of fundamental importance in transition metal geochemistry, particularly in mineral physics at high pressures and interpretations of visible to near-infrared spectra of minerals. Thus, the A °= R 5 relationship, eq. (2.17), is referred to frequently in later chapters. 

In the previous chapter it was shown how measurements of polarized absorption spectra in the visible to near-infrared region can provide information on such crystal chemical problems as oxidation states of transition metal ions, coordination site symmetries and distortions, cation ordering and the origins of colour and pleochroism of minerals. Much attention was focused in chapter 4 on energies of intervalence charge transfer transitions appearing in electronic absorption spectra of mixed-valence minerals. 

The conventional method for determining cation ordering and site populations within a crystal structure is by diffraction techniques using X-ray, electron and neutron sources. For determining site occupancies of transition metal ions, these methods have been supplemented by a variety of spectroscopic techniques involving measurements of Mossbauer, electron paramagnetic resonance (EPR or ESR), X-ray absorption (EXAFS and XANES), X-ray photoelectron (XPS), infrared and optical absorption spectra. 

Chapter 10 describes how spectral measurements of sunlight reflected from surfaces of planets, when correlated with experimental visible to near-infrared spectra of rock-forming minerals, have been used to detect transition metal ions, to identify constituent minerals, and to determine modal mineralogies of regoliths on terrestrial planets. 

More accurate force constants for a number of transition metal complexes with ammine ligands have been derived by normal-coordinate analyses of infrared spectra[130, 31l The fundamental difference between spectroscopic and molecular mechanics force constants (see Section 3.4) leads to the expectation that some empirical adjustment of the force constants may be necessary even when these force constants have been derived by full normal-coordinate analyses of the infrared data. This is even more important for force constants associated with valence angle deformation (see below). It is unusual for bond-length deformation terms to be altered substantially from the spectroscopically derived values. 

---