Electronic absorption spectra of tetrahedral oxoanions: Ferrate(VI) ion

Abstract

enhance tile Lewis basicity of tile adjacent nitrogen atom(:-~L It has further been shown that a band m the 2820-2700 cm region, presumably due to C-H stretching, should disappear upon coordination of this nitrogen to the metal ion<-+3L The absence of a band in this region in the 3,3-Me2Cz complex indicates coordination of the nitrogen atom attached to the methyl groups in this complex. Tile presence of an N(31 methyl group in 2,3-MeeCz would enhance the Lewis basicitv of this nitrogen. It is therefore assumed that this nitrogen is involved in coordination in its complex. Tile similar ligand [MeNHNMeCS2]-is coordinated 1241 through this nitrogen to nickel N(3) coordination is possible because the inductive effect of the methvl group may balance the lowering of electron density on this nitrogen atonl due to the phenyl group.The N-N stretching vibration has been assigned on the basis of earlier work (el and occurs at ca. Ill(Ill cm I ill Cz, vehcther the resulting group is chelated or not. Tile distiction between chelated and nonchelated carbazic acid has been made ~=~ only because this band broadens in the chelates. Tile presence of a slightly broad band m tile 1030-950 cm -J region in tile copper(ll ) complexes of N-substituted carbazic acids may taken its evidence for the nitrogen involvement in bond formation. AcknowledgementsThe author thanks the Director, Laboratorio di Tem-ia e Stuttura Electronica dei Composti Coordinazioni del CNR, Rome, italy, where part of the present work was cltrried ot, t. The CSIR and UGC. New Delhi are also thanked for financivl support.References <t~ A. Braibanti, G. Bigliardi, a. M. M. Lanfredi and A. Tiripicchio, Nature. 211, 1174 (1966). -<++I A. Braibanti, F. Dallavallc, M. A. Pellinghelli and F. Leporati, /non,,. ('hem.. 7. 14311 (1968). -~3~ A. K. Srivastava and F. Tarli, J. lnorg. Nuel. ('hem., ,?9. 1739 (1977) ('hem.. 5. 2236(1966).-~l>~ G. Base, R. L. Belford and R. E. Dickensen, bung. Chem., l, 438 (1962). -~1+, A. Chakravorty and S. Basu, J. lnoJ N. Nm'l. ('hem.. 17. 55 (IUhl). -iivj A. B. P. Lever, J. Lewis and R. S. Nyholm, J. ('hem. Sot,, 5262 (1962). -<ts~ K. Nakamoto, In./)'areal Spectra of Inorganic amt (',or(/imuion ('Oml~,uml,~, \Viler. New York (1%6). pp. 223. 233. -'"" K. Ilo and J. J. Zuckerman, Inorg. ('hem., 12. 1552 (1973). -c,,~ L. J. 13cl-lamy, J. Chem. Sot., 4487 (1954).(el~ G. F. Swatos, ('. Curran and J. P. Quagliano. J. Anl. ('hem. Sot., 77, 6159 (1955). -~e2~ R. F. Evans and W. Kynaston, ./. ('hem. 5oc.. 3151 (1963).-Ix~.l.F. Braunholtz. E. Ebsworth, F. Mann and N. Sheppard, J. ('hem. ,S'oc., 2780(1958. -le.u L, Gastaldi and P. Porta, ('rvst. ,~lrll('l. ('OIHPH.+ 4, 693 (1975). SummaryThe polarized electronic absorption spectrum of [FeOa] > has been measured at liquid heliunl tetnperature using single crystals of Ke('rO4 doped with the ferrate(Vl) ion and a new band has been observed at 9112 cm -I . An interpretation of the spectrum in the 9(11111-22(11)11 cnl i range is given by consMering tile possible ligand field transition under tile cr...

A new interpretation of the bonding and spectroscopy of the tetraoxoferrate(VI) FeO42− ion

“…The calculation of the absorption spectrum leads to a very good agreement with the features of the available experimental spectra both in the solid state and in solution, [7][8][9] but the assignments are very different from those accepted so far. This is naturally due to the different configurational bases which the Ligand Field Theory and ab initio quantum mechanical methods propose for modeling the bond and spectroscopy of these materials.…”

“…In addition, these triplets should lead to four electronic origins in each polarization, associated to the 2, 1, 1 AЈ components of 3 T 2 , 3 T 1 , and 3 E, respectively, with E ជ ʈb polarization and 1, 2, 1 AЉ with E ជ Ќb polarization, which in the experiment are not discerned, due to the lack of a sharp structure. 9 Instead, only one origin is detected in each polarization, which we interpret as the superposition of the components of the essentially degenerate 3 T 2 and 3 T 1 . In effect, the origin observed with E ជ ʈb polarization can be interpreted as resulting from the 2, 1 AЈ components of 3 T 2 and 3 T 1 , respectively, and that observed with E ជ Ќb polarization, from their 1, 2 AЉ components; their observed shift by 182 cm Ϫ1 , correlates very well with the energy difference which we find between 3 T 2 and 3 T 1 : some 200 cm Ϫ1 .…”

“…9,39 We have summarized the complex experimental data in the following way: In Table III the band maxima are tabulated and the maximum absorbance is indicated in squared parentheses, when available. Electronic origins are explicitly marked and the spacing of the progression that they initiate is given in parentheses, unless they are origins to several vibrational progressions; these data are not directly comparable with our vertical calculations, but contribute to give an idea of the whole band structure.…”

“…1 9 have detected two almost equally intense bands with electronic origins at about 16400 and 19700 cm Ϫ1 in parallel and perpendicular polarizations which exhibit the vibrational structure; the authors comment that the structure is not sufficiently sharp to reveal the crystal-site splitting due to the T d →C s distortion. In the same crystal with E ជ Ќb polarization, Brunold et al 7 observed a weakly structured band peaking at 17930 cm Ϫ1 , followed by a structured band showing a progression of 750 cm Ϫ1 .…”

“…Their relative intensities should be very different, since only the 3 A 2 → 3 T 1 electronic transition is electric dipole allowed in T d site symmetry and the observed T d →C s splittings are very small. As a matter of fact, the measured polarized absorption spectra [7][8][9] have been assigned accordingly, in spite of the fact that the broad absorption bands actually observed show intensities and complex structures which are hard to understand within the framework of the Ligand Field Theory without resorting to very significant mixings enabled by T d →C s distortion and spin-orbit coupling.…”