Vibrational spectra of complexes of norbornadiene with transition metals

Russian Chemical Bulletin -     

Mass spectra of arylhydroxyoximes and their complexes with transition metals

The EI mass spectra of several arylhydroxyoximes and of their coordinated complexes with transition metals, Cu, Ni, Co and Fe have been studied using high resolution mass spectrometry, metastable ion measurements and the stable isotopes ¹⁵N, ⁶³Cu and ⁶⁵Cu labelling to elucidate the fragmentation pathways. It has been found that the spectra of all compounds 1–24 except Fe-complex 24 show molecular ions. The relative intensity of molecular ions of the complexes, which contained the same kind of metal and the arylhydroxyoximes with different substituents R , is closely related to the electronegativity of R. In all metal-complexes 9–22 , the main decomposition pathways involve the successive loss of O, NO and then H₂O or LH. In these spectra the fragment ions of non-metal- containing species resulting from the cleavage of the dioxime ligands can be discriminated.     

Polyiodide amide complexes of transition metals: Structures and raman spectra

The Raman spectra of the polyiodide complexes of d elements with urea (Ur) and acetamide (AA), namely, [M(Ur)₆][I₃]₃ (M = Cr, Fe), Co(Ur)₆][I₃]₂ · 2Ur, [Mn(Ur)₆][I₈], [Ni(AA)₆][I₃]₂, [M(AA)₆][I₁₀ (M = Fe, Co, Cd), and [Co(AA)₄(H₂O)₂][I₁₂], are studied. The structure of [Cr(Ur)₆][I₃]₃ is studied. The crystals of [Cr(Ur)₆][I₃]₃ are monoclinic: space group C2/c, a = 15.260(5), b = 11.941(3), c = 20.506(6) Å, β = 106.14(3)°, Z = 4, V = 3589.4(18) ų. The I-I bond length in the CdI₂ · 4BA · 2I₂ polyiodide complex amorphous to X-rays is estimated by a correlation between the I-I bond length and the frequency of vibrations of this bond in the Raman spectra.     

The far-ultraviolet spectra of transition metal complexes

The intense bands which are found beyond the d-d bands in the electronic absorption spectra of transition metal complexes are usually assigned to intra-ligand or charge transfer transitions. However, Rydberg transitions originating with either the mainly 3d or ligand orbitals are also expected to contribute in this part of the spectrum. To explore this the vapor phase electronic absorption spectra of the tri-hexafluoroacetyl-acetonate complexes of Al, Sc, V, Cr, Fe and Mn have been recorded up to about 80000 cm^-1. In order to locate the Rydberg bands, quantum chemical calculations were carried out using the multiple scattering Xα MO method. Among the 4p and 4f type Rydberg bands there are several which are spin, Laporte, symmetry and angular momentum allowed and are expected to contribute strongly to the intensity observed in the ultraviolet and far-ultraviolet parts of the spectrum. The corresponding Rydberg states can mix, however, with valence-shell states of the same symmetry.The far-ultraviolet spectra of three sandwich compounds: bicyclopentadienyl Fe, Co and Ni were also determined. Due to the very low ionization potentials of these compunds, Rydberg transitions can contribute to the observed bands at rather low frequencies.     

Dihydrogen complexes of the transition metals

Summary The binding and activation of dihydrogen by simple transition metal complexes is of fundamental importance in processes as diverse as the homogeneous or heterogeneous hydrogenation of unsaturated organic molecules⁽¹⁾ and understanding how metalloenzymes such as nitrogenase⁽²⁾ and the hydrogenases⁽³⁾ work at the atomic level.Simple consideration of the oxidative-addition of dihydrogen to a coordinatively-unsaturated complex {or its reverse (reductive-elimination)} reveals that the reactions are compelled to proceed via a dihydrogen complex as shown in Equation (1). However until recently it was considered that the dihydrogen complex had only a fleeting existence. Although there had been some reports in the literature such as that by Ashworth and Singleton⁽⁴⁾ that the formally Ru^IV trihydride, [RuH₃(PMe₂Ph₂]⁺ was better formulated as the Ru¹¹ species [RuH(H₂)(PMe₂Ph)₂]⁺, these could not be substantiated. In 1984, though, Kubas showed that the apparently innocuous complex [WH₂(CO)₃(PPr ₃ ⁱ )₂] contained the side-on bonded dihydrogen molecule, established unambiguously by x-ray, and neutron crystallography and spectroscopy⁽⁵⁾. In this highlight the current status of dihydrogen complexes, their structure, identification and in particular their reactivity will be discussed.     

Norbornadiene complexes of transition metals

Conclusions Correlations were established between the stereochemistry of 2-(-carbinol)norbornadiene complexes of rhodium and their mass spectra.This study is also communication 30 from the series Mass Spectrometry of Transition Metal- Complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2701–2703, December, 1982.     

Composition and electronic spectra of some dimethyl sulfoxide complexes of transition metal ions

The dimethyl sulfoxide complexes of Cr(III), Mn(II) Mn(III), Fe(III), Co(II), Ni(II) and Cu(II) were obtained as their perchlorates and characterized by thorough chemical analysis and measurements of electronic spectra.The complexes are liable to incorporate extra dimethyl sulfoxide and perchloric acid beyond the composition M(DMSO)₆(ClO₄)_n. Dimethyl sulfoxide is comparable to urea regarding its spectrochemical and nephelauxetic strength     

Density functional calculations on electronic circular dichroism spectra of chiral transition metal complexes

Time-dependent density functional theory (TD-DFT) has for the first time been applied to the computation of circular dichroism (CD) spectra of transition metal complexes, and a detailed comparison with experimental spectra has been made. Absorption spectra are also reported. Various Co(III) complexes as well as [Rh(en)(3)](3+) are studied in this work. The resulting simulated CD spectra are generally in good agreement with experimental spectra after corrections for systematic errors in a few of the lowest excitation energies are applied. This allows for an interpretation and assignment of the spectra for the whole experimentally accessible energy range (UV/vis). Solvent effects on the excitations are estimated via inclusion of a continuum solvent model. This significantly improves the computed excitation energies for charge-transfer bands for complexes of charge +3, but has only a small effect on those for neutral or singly charged complexes. The energies of the weak d-to-d transitions of the Co complexes are systematically overestimated due to deficiencies of the density functionals. These errors are much smaller for the 4d metal complex. Taking these systematic errors and the effect of a solvent into consideration, TD-DFT computations are demonstrated to be a reliable tool in order to assist with the assignment and interpretation of CD spectra of chiral transition metal complexes.     

On the dioximine complexes of transition metals

Twelve new complexes NH₄[Co(DH)₂(SO₃)(amine)]·t H₂O (DH ₂=dimethylglyoxime) have been synthesized and characterized. Their i.r. spectra show the SO₃ to be co-ordinated to the Co atom through the S atom. The thermal decompositions of a series of derivatives of this type have been investigated with a derivatograph. The first process is an endothermic dehydration reaction, occurring in a single stage or in two successive ones. The loss of the crystallization water is followed by another endothermic reaction, without a clear stoichiometry, which is referred to as deamination. At higher temperatures, exothermic pyrolysis processes occur. From the TG curves, kinetic parameters have been derived for the dehydration and deamination reactions.

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Zusammenfassung Zwölf neue Komplexe der allgemeinen Formel NH₄[Co(DH)₂(SO₃)(amin)]·t H₂O (DH=Dimethylglyoxim) wurden synthetisiert und charakterisiert. Die IR-Spektren zeigen, daß SO₃ über das S-Atom koordinativ an das Co-Atom gebunden ist. Die thermische Zersetzung einer Reihe von Derivaten dieses Typs wurde mittels eines Derivatographen untersucht. Der erste Prozeß ist die in einem einzigen oder in zwei aufeinander folgenden Schritten verlaufende endotherme Dehydratisierung. Auf die Abgabe des Kristallwassers folgt eine andere endotherme Reaktion unklarer Stöchiometrie, die als Deaminierung bezeichnet wird. Bei höheren Temperaturen verlaufen exotherme Pyrolyseprozesse. Aus den TG-Kurven wurden kinetische Parameter für die Dehydratisierung und die Deaminierung bestimmt.

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NH₄Co(DH)₂(SO₃)(a)]·tH₂O, DH ₂ — . , . . , . «». . .

     

Thermodecomposition ofo-benzoquinone complexes of transition metals

Thermodecomposition of 3,5- and 3,6-di-tert-butyl-o-benzoquinone complexes of Cu, Fe, Co, Cr, Mo, and W has been investigated in the solid phase by the thermogravimetric method. The relative stability of a series of complexes has been determined from the temperatures at which their decomposition begins. Detachment of a neutral electron-donor ligand takes place in the first stage. Detachment of ano-quinone ligand and decomposition of theo-benzoquinone formed occur in the next stage. Thermodecomposition of Fe, Co, Cr, Mo, and W complexes gives oxides or carbides, while copper complexes decompose to pure metal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 327–329, February, 1994.     

The electronic spectra of argon-tetracene van der waals complexes

A simple relationship is shown to occur between spectral line position and the number of bound argon atoms in the electronic spectrum of argon-tetracene van der Waals molecules, in contrast to the conclusion of other workers. We show that bonding information may be obtained from such spectra.