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! A ' 1 lliiB»lilliiNHljilinl illliiHw lili : ' ' ' • ; '. ' ' ''•'•'' till 1 1 mSIS ii li t iiiis ikiii "' ' : - ,: n "''•' ' ,' r ' * ' ', < ', ', lit XI . j t i : 111/ fill './.;'. : '' '•"', .'' ; -^ ' II . Rittai««ifi!r»uii*ifj*M*fH**JH*jn : ' '' ''.' ' '"• : ' - mil \ . a I B R.APLY OF THE UNIVERSITY Of ILLINOIS 546 I #61 1966-1967 'VCtf Return this book on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. University of Illinois Library L161— O-1096 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/inorganicsemi196667univ IP \°l(jUk UNIVERSITY OF ILLINOIS Inorganic Chemistry Seminar Abstracts 1966-1967 TABLE OF CONTENTS PART I (Summer, 1966) Page Organometallic Exchange Reactions of Group III A Iky Is 1 Some Aspects Concerning Molecular Orbital Calculations .... k Interactions of the Perchlorate Anion 6 Extended Huckel Theory 11 The Donor Properties of Dimethyl Cyanamide 18 Magnetism in the Solid State —Electron Spin Resonance and Neutron Diffraction Studies 20 An Application of Extended Hiiakel Theory to Electron Density Distribution 25 The Metal-Metal Bond in Metal Atom Clusters and Polynuclear Compounds 27 PART II (September, 1966 thru May, 1967) Chemical Applications of Mossbauer Spectroscopy 1 Nuclear Magnetic Resonance Pseudocontact Shifts 6 Bonding and Structure in Metal Nitrosyls 10 Energy Level Ordering and Electron Distribution in n-Metallocene Complexes 15 Magnetic Properties of Metal Ammonia Solutions 18 Bonding in Transition Metal Fluoride Complexes 23 Optical Spectra of Some Transition Metal Ions in the Corundum Lattice 28 Properties of Complexes with Transition Metal-Group III A- or IV A -Metal Bonds 33 Electron Impact Studies of Organometallic Compounds: Bond Dissociation Energies 38 Recent Advances in Carborane Chemistry kk NMR Investigations of Some Metal Alkoxide Systems ^9 Homogeneous Catalysis of Isomerization and Specific Hydrogenation of Olefins 51 Nuclear-Electron Double Resonance. The Overhauser Effect ... 53 Molecular Beams 60 Chemistry and Structure of Allyl Complexes 62 Mass Spectrometry of Boron Hydrides 65 Bonding and Reactions of Coordinated Ligands in Metal Acetylacetonates 71 Factors Involved in the Stabilization of Pentacoordination in Complexes of Divalent Ni, Pd and Pt 76 (i) Page Cyclic Phosphines 79 Recent Studies of Peroxychroxnium Complexes 85 Recent Applications of Electrochemical Techniques to Inorganic Chemistry 88 Coordination Numbers in Chelate Complexes of the Lanthanide Ions 92 Electron Spin Resonance Studies of Simple Fluorine Containing Radicals 96 Sulfur Bridged Compounds and the Magnetic Exchange Interaction 101 Complexes of Derivatives of L-Cysteine 107 Laser Raman Spectroscopy 109 Applications of Crystal Field Theory to Spectra of Some Tetragonal Complexes 112 Substitution Reactions of Selected Triraeric Phosphonitrilic Chloride Derivatives: Thesis Report 118 (ii) - 1 - GRGANOMETALLIC EXCHANGE REACTIONS OF GROUP III ALKYLS Kenneth C. Williams June 27, I966 The nature of the association of the trialkyl derivatives of the metals of group III in solution has "been elucidated. It now appears that aluminum is the only member of this group whose saturated alkyl derivatives are associ- 1 2 ated in solution. Trimethylaluminum is dimeric in hydrocarbon solutions. Muller and Pritchard3 confirmed the bridge structure by the observation of two peaks in the nuclear magnetic resonance (n.m. r. ) spectrum of trimethylaluminum in cyclopentane at -75 °C. At room temperature they observed only one n.m. r. peak due to either intramolecular or intermolecular exchange of methyl groups. They estimated the Arrhenius activation energy for the exchange to be between 6 and 1^+ kcal/mole, and postulated that the exchange occurs by an intramolecular process. They suggested two possible mechanisms: (l) the breaking of one Al-C bond which may re-form with a different methyl group in the bridging positions or (2) the deformation of the molecule in which no bonds are broken, leading to a structure having four bridging methyl groups at the corners of a square. Ramey and co-workers4 did a more quantitative study on the tempera- ture dependence of the n.m. r. spectra of a number of aluminum alkyl dimers in an attempt to elucidate the mechanism by which the alkyl groups are transferred from the bridging to terminal positions. For (A1(CH3 )3)2 the enthalpy of activation for the exchange was found to be 15.6 i 0.2 kcal/mole. These authors postulated that the monomer was probably not formed as an intermediate but that the process is an intramolecular one involving the rupture of one Al-C bond, which then re-forms with a different alkyl group in the bridging position. Poole and co-workers have studied trialkylaluminum compounds using aluminum-27 n.m. r. They interpreted Muller and Pritchard' s data as an inter- molecular process according to the equation ki t (Al(CHs) 3 )g I 2 A1(CH3 ) 3 k-i Several investigators have studied the exchange of alkyl groups between mixed 4 6 7 trialkyls of aluminum. ' ' McCoy and Allred8 observed that methyl groups in solutions of trimethyl- aluminum and dimethylcadmium undergo a rapid intermolecular exchange at room temperature. By assuming a second-order process they were able to estimate an upper limit for the average lifetime of a methyl group before exchange. Mader and Evans 9 studied the intermolecular exchange of methyl groups in solutions of trialkylthallium compounds. They found that the exchange of methyl groups in trimethylthallium follows second-order kinetics and has an activation energy of 6.3 — 0.5 kcal/mole in toluene. Several investigations of exchange reactions of group III alkyls in basic 10 11 12 3 solvents have been conducted ' ' ' but all the systems discussed in this seminar will be concerned with hydrocarbon solvents. - 2 - (CH3 ) 3Ga-( (CH3 )sAl) 2 and (CII3 ) 3In-( (CH3 )3A1) 2 Systems in Cyclopentane The n.m.r. spectrum of a mixture of trimethylaluminum and trimethylgallium in cyclopentane consists of only a single peak at room temperature and, in view of the difference of chemical shifts of the pure compounds, indicates inter- molecular exchange of methyl groups. At -60°C three proton resonances are observed which corresponds to the trimethylaluminum bridge and terminal groups and trimethylgallium. The exchanges going on at room temperature may be represented as * Me Me Me Me Me Me _ , N ^Al" ^Al Me^ "^Me^ ""Me Me^ ""Me" ^Me 3- -x- Me Me Me Me Me Me Me Me Me Me "^Al" ^Al + ^Ga" >A1 ^Al" + ">' x Me'" ""Me "Me Me Me" ^Me" ^"Me Me The activation energy for the exchange of methyl groups of trimethylgallium and trimethylaluminum dimer is 15.9 -0.5 kcal/mole and the expression for the rate constant is given by the equation - * ^ ^T Me3Ga > rSSfa Due to the low solubility of trimethylindium in cyclopentane at low tempera- ture quantitative data could not be obtained for the system (CH3 ) 3In-(CH3 )3Al) 2 . However, some data on dilute solutions indicates the same kinetics are obeyed in the (CH3 ) 3Ga-( (CH3 )3Al) 2 system. (CH3 ) 3Ga-( (CH3 )3A1) 2 and (CH3 ) 3In-( (CH3 ) 3Al) 2 Systems in Toluene In toluene the kinetics were the same for both systems and the activation energies and the rate expressions were the same as in cyclopentane. It was also shown that the kinetics for the exchange of bridge and terminal groups in trimethylaluminum is the same in toluene and cyclopentane, and it was found that the exchange is independent of trimethylaluminum concentration. (CH3 ) 3Ga-(CH3 ) 3In System in Toluene Low-temperature studies on samples containing equal amounts of (CH3 ) 3Ga and (CH3 ) 3In showed no significant line broadening. This result indicates the exchange — (CH3 ) 3In + (CH3 ) 3Ga ; * (CII3 ) 3In + (CH3 ) 3Ga is very rapid and proceeds through a low-energy pathway, probably through a bimolecular process. i; • ' - 3 - REFERENCES 1. N. Muller and A. L. Otermat, Inorg. Chem., 4, 296 (1965), 2. K. S. Pitzer and H. S. Gutowsky, J. Am. Chem. Soc, 68, 2204 (1946). 3. N. Muller and D. E. Pritchard, ibid. , 82, 248 (i960). 4. K. C. Ramey, J. F. O'Brien, I. Hasegawa, and A. E. Borchert, J. Phys. Chem., 69., 3418 (1965). 5. C. P. Poole, Jr e , H. E. Swift, and J. F. Itzel, Jr., J. Chem. Phys., 42,(7) 2576 (1965). 6. E. G. Hoffman, Trans. Faraday Soc, jj8, 642 (1962). 7. H. Zeiss, "Organo-Metallic Chemistry," Reinhold Publishing Corp., New York, N. Y., i960, p. 208. 8. C. R. McCoy and A. L. Mired, J. Am, Chem. Soc, 84, 912 (1962). 9. J. P. Mader and D. F. Evans, J. Chem. Soc, 1963, 5534. 10. T. Mole and J. R. Surtees, Aust. J. Chem., 17, 310 (1964). 11. T. Mole and J. R. Surtees, Aust. J» Chem., 18, II83 (1965). 12. T. Mole and J. R. Surtees, Aust. J. Chem., 19, 381 (1966). 13. K. C. Williams and T. L. Brown, J. Am. Chenu Soc, in press. s -4- SOME ASPECTS CONCERNING MOLECULAR ORBITAL CALCULATIONS Anton Schreiner July 12, 1966 The prediction of molecular properties has long "been of interest to chemists. The several molecular orbital (MO) theories have been one approach, and aspects of some of these theories will "be discussed in this seminar along with new features and findings. The nature of MO calculations can be viewed as belonging to one of three levels. At the first level, one computes explicitly the expectation values of all electron-electron, electron-nuclear, and kinetic energy operators in Roothaan' 1 matrix element N M M ''.' = (n/k) + E E E C C [(nk/pq)(nq/pk)] nk (1) j=l p=l q=l pj qj where (nk/pq) = jx" (l) X (l) — X" (2) X (2)*dv (l)dv (2) (2) n R 1 and (n/k) = /x* (l) (- - E *a ) X (l)dv (1) (3) a C is defined by M = E C.
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  • Indium(III) Chloride – Catalyzed Michael Addition of Thiols to Chalcones : a Remarkable Solvent Effect

    Indium(III) Chloride – Catalyzed Michael Addition of Thiols to Chalcones : a Remarkable Solvent Effect

    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Publications of the IAS Fellows Issue in Honor of Dr. Rama Rao ARKIVOC 2005 (iii) 44-50 Indium(III) chloride – catalyzed Michael addition of thiols to chalcones : a remarkable solvent effect Brindaban C. Ranu,* Suvendu S. Dey, and Sampak Samanta Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta – 700 032, India E-mail: [email protected] Dedicated to Dr. A. V. Rama Rao on the occasion of his 70th birthday (received 28 Aug 04; accepted 23 Sep 04; published on the web 26 Sep 04) Abstract Indium(III) chloride in methanol efficiently catalyzes Michael addition of aromatic and aliphatic thiols to chalcones and related compounds. This reaction is remarkably solvent selective and it does not proceed in conventional solvents such as tetrahydrofuran, methylene chloride and water. Keywords: Michael addition, thiol, chalcone, indium(III) chloride, solvent effect Introduction The Michael addition of thiols to electron deficient alkenes is a very useful process for making carbon-sulfur bond. This addition to chalcone derivatives is very interesting and challenging as it is less facile compared to the addition to aliphatic acyclic enones and thus it is not always satisfactory with the conventional reagents used for general 1,4-addition. Recently, a number of 1a procedures involving a variety of catalysts such as synthetic diphosphate Na2CaP2O7, natural 1b 1c 1d phosphate, InBr3, fluorapatite, have been reported. Indium halides, particularly indium(III) chloride have emerged as a potent Lewis acid for various organic transformations in recent times.2 As a part of our interest in indium(III) chloride 3 catalyzed reactions we discovered that although InCl3 has been used in the Michael addition of silylenol ethers,4a amines,4b pyrroles4c and indoles4d to electron-deficient alkenes no report has been found demonstrating the use of InCl3 for addition of thiols to chalcones and related systems.