Electronic Spectral Study

Besides the electronic spectral studies noted above, we have also carried out in situ studies of the acidic ruthenium catalyst using nmr and infrared spectral techniques. A key set of observations derive from the and 13C nmr spectra of an operating catalyst at 90° and Pco 1 atm which indicate the presence of only one major ruthenium species. The proton spectrum shows a sharp singlet at 24.0 T which remains such when the solution is cooled to room temperature, although the slow formation of other species was observed over a period of hours at the latter conditions. The 1H-decoupled 13C spectrum of the... 

Regarding the study of these complexes by various physical techniques, only IR spectroscopy has been widely used so far. Only a few X-ray structural, electronic absorption, and fluoresence emission spectral data are available. Other methods such as ESR (especially of Gd(III) complexes), NQR, and Mossbauer (especially of Eu-151) have not been seriously applied for the study of these complexes in the solid state. In solution, only conductance studies have attracted attention NMR, dipole moment, and electronic spectral studies are few in number. The lack of physical data limits our understanding of the structure and bonding in these complexes. In future, when more interest is evinced in applying various physical techniques to study these complexes, one may hope to come across more interesting and useful revelations. 

F = 1.816 A) and neutron diffraction (Os—F = ture of [OsFg] has also been studied by electron diffraction and ab experimental Os—F distance is 1.828 A. The electronic spectral study of [OsFg] has been reported. The compound (NO)[Os(F)v] has also been mentioned in CCC (1987). 

With bidentate SBs, monomeric [VO(SB)2] complexes are normally formed. On the contrary, with tridentate dibasic SBs, dimeric species often form. It appears that the dibasic character of the ligands forces the VOz+ ion to dimerize leading to anomalous magnetic properties. Proposed structures have not been verified owing to their non-crystalline nature. Insolubility precluded molecular weight determinations and ESR and electronic spectral studies have been carried out in the solid state only. 

Detailed electronic spectral studies for Mo02C12 and Mo02Br2 have been performed (ref. 

Since the first report of the sulfur-addition reaction to 1,1-dithio complexes (156), a number of structural studies have verified the originally proposed ring expansion of the MS2C ring following this reaction. In addition, mechanistic studies on the sulfur insertion reaction and electronic spectral studies of the perthiocarboxylate Ni(II) complexes have been reported. 

Initial studies with l,3-bis-[phenyl-(o-diphenylphosphinophenyl)-arsinojpropane (P2as2) by MoAuliffe (28) have led to the isolation of the diamagnetic planar [Ni(p2asa)] (C104)a and the purple [Ni(paaSa)X]-BPh4 (X = Cl, Br, I) complexes. The latter have been assigned square-pyramidal coordination about the nickel atom, on the basis of electronic spectral studies. 

Dinuclear Fe"-Cr" complexes with a bridging cyano ligand have been prepared and characterized by i.r. and electronic spectral studies. The complexes isolated were [(CN)5Fe-CN-Cr(H20XNH3)J and [(CN)sFe-CN-Cr(NH3)5]H20. 

Chromium v). Ab initio MO calculations and electronic spectral studies on the CrO group show that the second lowest energy electronic absorption is due to an oxygen-metal charge transfer rearrangement within the CrO " group. ... 

XYfi-type molecule is XtF. In their earlier work, Claassen et al suggested the distortion of XeF from Oi, symmetry since they observed two stretching bands in infrared and three stretching bands in Raman spectra. It was not possible, however, to determine the precise structure of XeFe until they carried out a detailed infrared, Raman and electronic spectral study of XeFe vapor as a function of temperature. They were then able to show that XeF consists of the three electronic isomers shown in Fig. 11-17, and to explain subtle differences in spectra at different temperatures as a shift of equilibrium among these three isomers. As expected, the isotope shift of the... 

G.l.c. retention data over a ran of temperatures have been measured for Cr(hfa)3, Cr(tfa)3, and several other such chelates in three liquid phases and, together with other solution-phase data, have been used to show that the behaviour of these complexes in the liquid phase is determined solely by nonspecific van der Waals-type forces. " The electrophilic substitution reactions of fluorinated P-diketonato-chromium(iii) complexes have been studied under controlled conditions and the results obtained were shown to support the quasi-aromatic character of the six-membered chelate ring. Seven new tris(P-diketonato)chromium(iii) complexes have been prepared and characterized by magnetic, i.r., and electronic spectral studies. ... 

---