Chemistry remains an experimental science. The theory of chemical bonding leaves much to be desired. Yet, the past 20 years have been marked by a fruitful symbiosis of organic chemistry and molecular orbital theory. Of necessity this has been a marriage of poor theory with good experiment. Tentative conclusions have been arrived a t on the basis of theories which were such a patchwork on approximations that they appeared to have no right to work; yet, in the hands of clever experimentalists, these ideas were transformed into novel molecules with unusual properties. In the same way, by utilizing the most simple but fundamental concepts of molecular orbital theory we have in the past 3 years been able to rationalize and predict the stereochemical course of virtually every concerted organic reaction.' In our work we have relied on the most basic ideas of molecular orbital theory-the concepts of symmetry, overlap, interaction, bonding, and the nodal structure of wave functions. The lack of numbers in our discussion is not a weakness-it is its greatest strength. Precise numerical values would have to result from some specific sequence of approximations. But an argument from first principles or symmetry, of necessity qualitative, is in fact much stronger than the deceptively authoritative numerical result. For, if the simple argument is true, then any approximate method, as well as the now inaccessible exact solution, must obey it. The simplest description of the electronic structure of a stable molecule is that i t is characterized by a finite band of doubly occupied electronic levels, called bonding orbitals, separated by a gap from a corresponding band of unoccupied, antiboding levels as well as a continuum of higher levels. The magnitude of the gap may range from 40 kcal/mole for highly delocalized, large aromatic systems to 250 kcal/mole for saturated hydrocarbons. It should be noted in context that socalled nonbonding electrons of heteroatoms are in fact bonding. Consider a simple reaction of two molecules to give a third species, proceeding in a nonconcerted manner through a diradical intermediate I. A + B + [I] + C

The Conservation of Orbital Symmetry (福井謙一とフロンティア軌導理論) -- (参考論文)

Structural characterization of copper–indium chalcopyrite precursors (PPh3)2CuIn(ER)4 [R=CH3, E=S and R=Ph, E=S and Se]

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogens interact with the CS2 carbons with a bond order near two; the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. A preliminary thermolysis study of the homoleptic species res...

Structural characterization and preliminary decomposition study of four unsymmetrically substituted nickel dithiocarbamate complexes

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. Synthetic, spectroscopic, structural, thermal, and sulfide materials studies are discussed in light of prior literature. The spectroscopic results are routine. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogen atoms interact with the CS2 carbons with a bond order of about 1.5, and the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. Thermogravimetric analysis of the homoleptic species under inert atmosphere is consistent with production of 1:1 nickel sulfide phases. Thermolysis of nickel dithiocarbamates under flowing nitrogen produced hexagonal or -NiS as the major phase; thermolysis under flowing forming gas produced millerite (-NiS) at 300 C, godlevskite (Ni9S8) at 325 and 350 C, and heazlewoodite (Ni3S2) at 400 and 450 C. Failure to exclude oxygen results in production of nickel oxide. Nickel sulfide phases produced seem to be primarily influenced by processing conditions, in agreement with prior literature. Nickel dithiocarbamate complexes demonstrate significant promise to serve as single-source precursors to nickel sulfides, a quite interesting family of materials with numerous potential applications.

/pdf/synthesis-structure-characterization-and-decomposition-of-4sqn6yi74m.pdf

Synthesis, Structure, Characterization, and Decomposition of Nickel Dithiocarbamates: Effect of Precursor Structure and Processing Conditions on Solid-State Products

Structure and properties of 9,10,11,12,13,14-hexahydro-9,10[1′,4′]-benzenoanthracene and 9,10,11,12,13,14,15,16-octahydro-9,10[1′,4′]-benzenoanthracene

9,10,12,13,14,15-Hexahydro-11H-9,10[1′,3′]cyclopentanthracene in two modifications

The compound 9,14,15,16,17,18,19,20-octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene, C28H24, was prepared by hydrogenation of the photocycloadduct of dibenz[a,c]anthracene and 1,3-cyclohexadiene with Pt/C in ethyl acetate. The X-ray diffraction analysis shows that the compound crystallizes in the monoclinic space group with the geometric parameters of = 11.0090(17) A, = 13.733(2) A, = 13.091(2) A, and = 109.583(13)°. In addition to several close intramolecular contacts involving hydrogens derived from the dibenzanthracene moiety, long interannular C–C single bonds of about 1.593 A are present. These bonds are shorter by about 0.18 A than the corresponding bonds in the unsaturated precursor, which can be attributed to reduced strain in the more saturated polycyclic ring system. Anisotropic shielding of the four endo-methylene hydrogens in the 1H NMR spectrum is larger for the two hydrogens lying above the phenanthrene unit, which resonate at 1.03 ppm, than those above the benzenoid ring, which resonate at 1.24 ppm. Theoretical calculations reproduce the geometry with good agreement.

/pdf/structure-and-properties-of-9-14-15-16-17-18-19-20-octahydro-4swtg5ktgh.pdf

Structure and Properties of 9,14,15,16,17,18,19,20-Octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene

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9,10,12,13,14,15-Hexahydro-11H-9,10[1′,3′]cyclopentanthracene in two modifications

Structure and properties of 9,10,11,12,13,14-hexahydro-9,10[1′,4′]-benzenoanthracene and 9,10,11,12,13,14,15,16-octahydro-9,10[1′,4′]-benzenoanthracene

Structure and Properties of 9,14,15,16,17,18,19,20-Octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene