Ligand modes

Table 9.4 Assignment of vibrational iron-ligand modes based on a DFT calculation on the model with 21 atoms...

The anionic bis-ylide compounds [R2P(CH2)2] bonded as bridging ligands (mode VI) have been extensively studied in complexes of coinage metals, mainly... 

The Ni-ligand mode can be identified as the Ni-axial ligand stretch because of the close analogy between the Ni isotopic substitution results and the Fe-isotope substitution data for native hemoglobin and myoglobin (27-30). For the native proteins myje complete isotope substitution studies including N- N... 

Table 8. Prominent satellites of high-frequency vibrational ligand modes found in the T = 1.3 K emission spectra of Pt(2-thpy-h(j)2, Pt(2-thpy-h(j)(2-thpy-d5), and Pt(2-thpy-d5). All satellites belong to the respective electronic origin P...

The important problem of metal-nitrogen frequencies is unlikely to be resolved without at least a vibrational analysis of the ligands (no easy task) more extensive Raman data would also help. It has, in fact, been suggested that the bands discussed above are possibly ligand modes excited on complex formation (162), although it is not clear why this should occur so randomly. Tentative assignments of r(MN) above 200 cm have been made for a number of bipyridyl and phenanthroline complexes (e.g., 253, 254, 452, 502). 

The r dependence of the relative resonance Raman intensities of two modes is much more sensitive to their difference in frequency than to their difference in displacement. The reason for this dependence is found in the short time dynamics of the wavepackets which is much more sensitive to the frequency at a given displacement than to the displacement for a given frequency. This simple physical picture provides an explanation for why very low frequency metal-ligand modes in a big molecule often do not appear in the resonance Raman spectrum even though the modes have appreciable displacements. 

Both pyridazine- and phthalazine-derived ligands show a very similar coordinating behavior to metal ions. It is has been observed that in most of their metal complexes the diazine (N-N) group bridges two metal in a //12 fashion (mode 1), but in some cases the diazine (N-N) behaves as a mono-dentate ligand (mode 2) (Figure 1). 

Metal-ligand modes were identified by resonance Raman spectroscopy, and assigned after a normal coordinate analysis, for Mn2(0)(0Ac)2(bipy)2 (H20)2.24° Resonance Raman spectra of MnN(P), where P = a range of porphyrins, included vMn=N near 1050 cm-1.241 The IR spectra of Min(P)Cl, Mn(P), where M111 = Mn, Fe Mn = Co, Ni, Cu, Zn, P = meso-tetra-(4-myristyloxy-phenyl)porphyrin, included vMnN (coupled with a porphyrin deformation mode) at 250 cm 1, and vMninCl 320 cm 1.242... 

The IR and Raman spectra of (1) show characteristic bands of terminal and 7i-bonded, bridging aryl groups, both in the solid state and in solution.4 The Raman spectrum of uranocene, U(COT)2, at 77 K, gave ligand mode assignments, e.g. vCH at 3042 cm-1 and vCC at 1500 cm-1.5... 

Table 1 Ligand mode assignments for CpRu( PPhf 2SnX2Y (/cm 1)...

The complex (26) shows vCCC as a strong IR band at 1924 cm-148 Ligand mode assignments were proposed from the IR spectrum of Os2(CO)x(p.2 rl1 -... 

TR3 spectra were used to obtain data on the ligand modes of both high- and low-spin isomers of [Fe(L)]2+, where L = /V,/V,/V, /V -tetrakis(2-pyridylmethyl)-6,6,-bis(aminomethyl)-2,2 -bipyridine or V,V -bis(benzyl)-7V,7V -bis(2-pyridyl-methyl)-6,6,-bis(aminomethyl)-2,2 -bipyridine.193 Resonance Raman and TR3 data were used to obtain detailed ligand mode information for Ru(bi-py)2(dpp)2+ and (bipy)2Ru(dpp)Ru(bipy)24+, where dpp = 2,3-bis(2-pyridyl)-pyazine, and their bipy-d8 analogues.194 A resonance Raman study has been carried out on electronic communication and delocalisation in complexes involving two Ru3 clusters linked by a pyrazine ligand.195... 

The IR and Raman spectra of MLnI2, where M = Ni, n = 4 M = Zn or Cd, n = 2, L = m-methylaniline, gave quite detailed ligand mode vibrational assignments.197 The IR spectra of platinum(II) complexes in carbamide and carbamide-halide melts show the formation of Pt(NH3)42+ on dissolution of (NH4)2[PtCl4], as well as Pt(NH3)X3 in the presence of NH4+X, where X = Cl or Br.198 Picosecond-scale TRIR spectroscopy was used to probe the dynamics of the lowest excited state of Pt(bipy)(4-CN-C6F4-S)2.199... 

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