Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)

Abstract

FragmentsChains, rings, substituents-those are the building blocks of the marvelous edifice of modern organic chemistry. Any hydrocarbon may be constructed on paper from methyl groups (CH,), methylenes (CH,), methynes (CH), and carbon atoms (C). By substitution and the introduction of heteroatoms all of the skeletons and functional groupings imaginable, from ethane to tetrodotoxin, may be obtained.The last thirty years have witnessed a remarkable renaissance of inorganic chemistry, and the particular flowering of the field of transition-metal organometallic chemistry. The complexes 1-9 are a selection of some of the simpler creations of the laboratory in this rich and ever-growing field. I Structures 1-3 illustrate at a glance one remarkable feature of transition-metal fragments. Here are three tricarbonyliron complexes of organic moieties-cyclobutadiene, tri methylenemethane, and 1 -hydroxy-1,3-butadienewhich on their own would have little kinetic or thermodynamic stability. Yet complexed to Fe(CO), these molecules are relatively stable: they exist in a bottle. The inorganic [**I Copyright 0 The Nobel Foundation 1982. We thank the Nobel Foundafragment is not merely a weakly attached innocent bystander: it transforms essentially and strongly the bonding relationships in the molecule.Structures 4-6 contain the ubiquitous cyclopentadienyl ligand (Cp), two of them in the archetypical ferrocene, one in CpMn(CO),, two bent back in Cp,Ti(CO),. Structures 7-9 introduce us to the simplest representatives of the burgeoning class of clusters-assemblages of two or more metal atoms embellished with external ligands. If we seek order, unity, a way of thinking about these complexes, it is not difficult to perceive that the molecules contain as building blocks transition metal-ligand fragments, ML,, such as M(CO),, M(CO),, M(CO),, or MCp. It must be said immediately that there is nothing special about the carbonyl ligand. It is merely a representative and common component of organometallic complexes. Phosphanes, olefins, alkyls will d o as well.To reconstruct the complexes 1-9, we need to know the electronic structure of the fragments. For the simple qualitative picture of the bonding in these molecules that we seek, we d o not need to know every last detail of the electronic structure of each molecule. It will suffice that we know the frontier orbitals of the fragments-the higher occupied and the lower unoccupied levels-in other words the valence active orbitals of each fragment. It is Kenichi Fukui who taught us the importance of the frontier orbitals. We shall soon see that it is the resemblance of the frontier orbitals of inorganic and organic moieties that will provide the bridge that we seek between the subfields of our science.Over the last eight years my coworkers and I have built up a library of the orbitals of ML, fragments['-31. We have done so using entirely qualitative, approximate molecular orbital calculations of the extended Huckel type (a procedure for its time, developed with another of my teachers, William N ...

Symmetry Breaking in NMR Spectroscopy: The Elucidation of Hidden Molecular Rearrangement Processes

“…Molecular orbital calculations [28] revealed that the rearrangement proceeds via a "modified windscreen-wiper" motion (Scheme 9), analogous to that previously proposed for the isolobal C 5 H 5 + nido cluster [29,30]. Note that simple circumambulation of the alkyne round the periphery of the metal triangle (Scheme 10) does not racemize the cluster.…”

“…The 3:1 ratio of silicon environments in 32 is very clearly shown in Figure 12 which depicts its two-dimensional 1 H- 29 Si shift-correlated NMR spectrum. The unit intensity 29 Si resonance connects only to the protons in the RRR and SSS isomers, whereas the triple intensity peak correlates only with the other combinations.…”

Exchange and correlation energy in density functional theory: Comparison of accurate density functional theory quantities with traditional Hartree–Fock based ones and generalized gradient approximations for the molecules Li2, N2, F2

“…We wish to stress that the properties of the KS orbitals make them particularly suitable for use in the molecular orbital theories of chemistry. 53,54 For atoms LDA is known to underestimate the exchange energy by roughly 10% and it overestimates the correlation energy by roughly 100%. The present examples demonstrate this to be true for molecules as well.…”

The Application of the 4n Series Method to Categorize Metalloboranes

“…The cluster complexes used have been taken from a wide spectrum of sources but mostly from the work by Fehlner and Grimes (Fehlner, 2002;Callahan, et al, 1974;Grimes, 1974). In addition, the vital isolobal relationship between transition metals and main group elements will be utilized (Hoffmann, 1982;Kiremire, 2015a). The relationship is summarized below.…”