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33is PROCEEDINGS XVIIT INTERNATIONAL CONFERENCE ON COORDINATION CHEMISTRY •July 18-23,' 1977 Sao Paulo, Brazil PROCEEDINGS XVIII INTERNATIONAL CONFERENCE ON COORDINATION CHEMISTRY July 18-23, 1977 Sao Paulo, Brazil Sponsors Brazilian Academy of Sciences International Union of Pure and Applieu Chemistry University of Sao Paulo XVIII ICCC SCIEN1 Scope Organized by Brazilian Academy of Sciences will 1 Organizing Committee P. Senise, Sao Paulo (Chairman) E. Giesbrecht^ Sao Paulo S. Mathias, Sao Paulo L. Hainberger, Rio de Janeiro A.C. Spinola Costa, Bahia E.3. Paniago, Belo Horizonte N. Valle Silva, Rio de Janeiro (Treasurer) Krumh Local Executive Committee P. Kr P. Senise (Chairman) E. Giesbrecht S. Mathias (Editor) G. Vicentini O.A. Serra Plena H. Li Chum Appli SCIENTIFIC PROGRAM Scope Plenary lectures, section lectures and contributed papers will be presented under five topics: I - Organometallic Compounds II - Mechanisms of Reactions of Complexes III- Structure and Stereochemistry of Coordination Compounds IV - Application of Coordination Compounds in Ana- lytical Chemistry V - Lanthanide Chemistry Krumholz Memorial Session A special session honoring the memory of the late Professor P. Krumholz will be held on Tuesday, July 19, 1977. Plenary lectures will be published in the IUPAC Journal Pure and Applied Chemistry. The Monc 11:1 E.O. Prep plea Tues 11:1 H. T Che Thu PLENARY LECTURES 11: S. The con Thu 17: H.M App Fri 11: E. Coo (X- --••, n.ira^ The plenary lectures will take place in Room A Monday, July 18,1977 11:15 - 12:15 h E.O. Fischer, Munich (GFR) Preparative and structural aspects of transition metal carbyne com- plexes Tuesday, July 19, 1977 11:15 - 12:15 h H. Taube, Stanford (USA) Chemistry of ruthenium (II) and osmium (II) ammines Thursday, July 21, 1977 11:15 - 12:15 h S. Kirschner, Detroit (USA) The pfeiffer effect, outer-sphere complexation, and the absolute configuration of coordination compounds Comb" Thursday, July 21, 1977 17:00 - 18:00 h vari H.M.N.H. Irving, Leeds (UK) Application of coordination compounds in analytical chemistry disc of t Friday, July 22, 197-7 11:15 - 12:15 h An o E. Giesbrecht, Sao Paulo (Brazil) Coordination compounds of rare earths with QnX+O type ligands meta (X=S,N,P,As) cati —j >• •"' PREPARATIVE AND STRUCTURAL ASPECTS OP TRANSITION METAL CARBTNE COMPLEXES E.O.Fischer Institute of Inorganic Chemistry, Technical University Munich, Arcisstrasee 21, D-8000 MUnehen 2, Germany A short introduction deals with the discovery of the first capbyne complexes of the type trans-Hal(CO)^MCR ( Hal = Cl, Br, Ij M • Cr, Mo, W; R = methyl, phenyl) in 1973, defined by its name as having a sp hybridised, carbon atom triply bonded to a transion metal. A general survey then follows about presently known routes, to prepare carbyne complexes of uncharged and also ionic types, how t& modify them, and how to use them as starting materials for the introduction of the carbyne ligand into organic chemistry. Examples will be mentioned especially for a) CO substitution, b) halogen substitution, c) additions of nucleophiles to the crb e' d) CR-substitution, e) preparation of organic molecules which contain the cleaved CR-ligand. Combined with the preparative results x-ray structures of a great variety of such uncharged and cationic carbyne complexes will be discussed, and their importance for the determination of radii of triple bonded transition metals will be emphasized. An outlook for the preparation of new carbene complexes of transition metals, based on addition reactions of anionic nucleophiles to cationic carbyne complexes, will complete the aspects of the field. ^CHEMISTRY OF RUTHENIUM(II) AND OSMIUM(II) AMMINES Henry Taube Department of Chemistry, Stanford University Stanford, California 94305 A motivation for the study of ruthenium(II) and osmium(II) ammines is that back-bonding is an important interaction in the complexes containing also unsaturated ligands. The pentaammine-unsaturated ligand species are usually substitution inert, a property which facilitates their characterization and so they provide a convenient opportunity for studying the interface between ligands which are regarded as characteristics of organometallic compounds, and the saturated ligands which figure in the chemistry of "classical" complexes. Thoy provide, as well, an opportunity for studying in a systematic way the effects of back donation on physical properties and reactivity. The chemistry of the ruthenium ammines has been the more thoroughly studied, and some of the salient observations made with them will be reviewed. Comparisons will be made with Fe(CN)_?~ (referred to by J. Malin as the poor man's ruthenium) and with Os(NEL) 2+. The osmium(II) ammines call for more elaborate preparative procedures than suffice for ruthenium(II) ammines, and current research on these complexes will be described. ,-vnJj.Ji^ Z/ THE PFEIFFER EFFECT, OUTER-SPHERE COMPLEXATION, AND THE $7 "APP1 ABSOLUTE CONFIGURATION OF COORDINATION COMPOUNDS H.M Stanley Kirschner Department of Chemistry, Wayne State University Detroit, Michigan 48202 U. S.A. The Pfeiffer Effect is the change in optical rotation of a solution of one enantiomer an optically stable compound (called the "environment" substance) upon the addition of a racemic mixture of an optically labile complex compound. The nature of the Effect will be described, along with evidence supporting the "equilibrium displacement" mechanism proposed for the Effect. Further, the effect of Pfeiffer activity on the racemization and resolution of dissymmetric complexes is described, along with the application of the Pfeiffer Effect to the determination of absolute configuration of coordination compounds which are both optically active and optically labile. Still further, a proposal to describe the basic nature of the Effect at the molecular level is presented, which utilizes the concept of hydrogen bonding of the environment substance to pi-electron cloud systems of the ligands of the complex. With regard to dissymmetric, optically stable complexes, it has been shown that an interaction occurs between such complexes and environment substances when the latter are present in much higher concentrations than the former. A technique will be described which utilizes this phenomenon to predict the absolute configuration of dissymmetric, optically stable complexes, which is base.: upon a proposal of outer-sphere complexation through hydrogen bonding between the optically active environment substances and the ligands of the complexes. V / 7i "APPLICATIONS OF COORDINATION COMPOUNDS IN ANALYTICAL CHEMISTRY" C001 H.M.N.H.Irving TYP3 Erni Department of Inorganic and Structural Chemistry, University of Leeds, Leeds LS2 9JT, England and Department of Chemistry, Ins" University of Cape Town, Cape Town, South Africa. Cai: 0101 Coordination compounds have been used extensively in analytical chemistry for over 100 years. Examples of applications in absorptiometry, atomic absorption spectroscopy, chromatography (gas-solid, liquid-solid, high-pressure and tic), gravimetry, liquid-liquid extraction and titrimetry (especially complexometry), for separation and preconcentration, for ion-selective electrodes, and for the design of highly selective reagents will emphasise those characteristics (e.g. polarity, size, colour, hydrophobicity, stability, conformation etc.) relevant to particular uses. Examples of useful steric effects, of synergism and kinetically controlled separations will be included. COORDINATION COMPOUNDS OF RARE EARTHS WITH Q X TYPE LIGANDS (X = S, N, P, As). Ernesto Giesbrecht Instituto de Quimica, Universidade de Sao Paulo Caixa Postal 20780 01000 - Sao Paulo, SP, Brazil An increasing number of complexes formed by rare earths with Q X -»• 0 type ligands are being reported in the literature. Sulphoxides, phosphine oxides and heterocyclic-N-oxides are the more important representatives of these typs of coordinating agents although some complexes of seleno1oxides and arsine 1 oxides are also described. The preparation, the properties and the more impox^tant physical and chemical characteristics will be reported. SECTION LECTURES M. To The t (Room Thurs 10:20 1 t MICROCOPY RIMHUIDN II si l Il/Uil 10 Monday; July 18', 19 77 14:00 - 14:30 h E.Fluck, Struttgart (GFR) Prussian blue and its analogs (Room A) . Monday, July 18, 1977 16:00 - 16:30 h B.J.-Trzebiatowska, Wroclaw (Poland) Antiferromagnetic and ferromagnetic phenomena and structure of coordination compounds (Room B) Monday, July 18, 1977 17:20 - 17:50 h L. Sacconi, Florence (Italy) Recent contributions to the chemistry of 3d metals in low oxidation states (Room A) Tuesday, July 19, 1977 10:20 - 10s50 h u.A. Koningstein, Ottawa (Canada) Eletronic Raman spectroscopy of some transition metal sandwich compounds {Room D) Tuesday, July 19, 1977 17:20 - 17:50 h M. Tobe,London (UK) The trans effect. Some recent kinetic and equilibrium studies (Room C) Thursday, July 21, 1977 10:20 - 10;50 h R.C. Mehrotra, Delhi (India) Coordination chemistry of lanthanides (Room C) i ii •! ijt Y; 11 Thursday, July 21, 1977 PRUSSIAN B 15:00 - 15:30 h E. Fluck a G. Eichhorn, Baltimore (USA) Recent studies on the effect of metal ions on nucleic acid and Institute genetic information transfer Pfaffenwal Thursday, July 21, 1977 A survey i 16:20 - 16:50 h and bondin J. Chatt, Brighton (UK) The reactivity of dinitrogen in its stable complexes [(C) (Room C) ml C6 New result Friday, July 22, 1977 10:20 - 10:50 h which have S.L. Davydova, Moscow (USSR) Atomic absorption spectrophotometric analysis of coordination with vfi = compounds with and without preliminary decomposition (Room C) bauer spec iron and t Friday, July 22, 19 7 7 Mossbauer 14:00 - 14s30 h F.G. Gallais, Toulose (France) Charge transfer in coordination compounds: a study of Lewis coordinate acids of group III elements by means of nuclear resonance spectroscopy (NMR and NQR) Furthermor (Room A) spectrosco Friday, July 22, 1977 the type F 16:00 - 16:30 h discussed. S.P. Sinha, Zurich (Switzerland) Application of the "inclined W" theory in predicting the sixth and the higher ionization potentials for the lanthanide series (Room D) —.•j».^a^A jy / ANTIFERPf COORDINAT V 12 B.
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  • Wavelength Dependence of Photooxidation Vs Photofragmentation of Chromocene

    Wavelength Dependence of Photooxidation Vs Photofragmentation of Chromocene

    J. Phys. Chem. A 2001, 105, 8665-8671 8665 Wavelength Dependence of Photooxidation vs Photofragmentation of Chromocene Peter T. Muraoka, Daniel Byun, and Jeffrey I. Zink* Department of Chemistry and Biochemistry, UniVersity of California, Los Angeles, California 90095 ReceiVed: March 19, 2001; In Final Form: July 2, 2001 Photooxidation and metal-ligand photolysis reactions of bis(cyclopentadienyl)chromium, chromocene, in the range 24 390-15 630 cm-1 are studied in the gas phase by using time-of-flight mass spectroscopic detection. Photooxidation of the intact chromocene molecule unexpectedly dominates in the range 23 530-24 000 cm-1. The relative importance of photooxidation compared to photofragmentation is strongly wavelength dependent. A prominent species at all wavelengths is the chromium ion, but in a wavelength region corresponding to the lowest energy ligand to metal charge transfer excited electronic state absorption, the strongest peak is from the chromocene ion. The excitation spectra are reported for three selected species: chromocene ion, mono- (cyclopentadienyl)chromium ion, and the chromium ion. The spectrum obtained by monitoring the metal ion contains sharp peaks that are assigned to neutral chromium atom resonances. Sharp losses of intensities in the molecular ion spectra are observed at these wavelengths. The wavelength dependencies of the photoreactions are interpreted and explained in terms of the identity of the initially populated excited electronic state and the ionization energy of the molecule. When the initially populated excited electronic state is the ligand to metal charge transfer state, the first photon causes minimal bond weakening and the second photon excites the intact chromocene above the ionization energy, resulting in efficient ionization of the parent molecule.