A New Look at Structure and Bonding

A new look at structure and bonding in transition metal complexes. J. K. Burdett, Adv. Inorg. Chem. Radiochem., 1978, 21,113-146 (73). 

A New Look at Structure and Bonding in Transition Metal Complexes Jeremy K. Burdett... 

A NEW LOOK AT STRUCTURE AND BONDING IN TRANSITION METAL COMPLEXES... 

Qualitatively, the resonance picture is often used to describe the structure of molecules, but quantitative valence-bond calculations become much more difficult as the structures become more complicated (e.g., naphthalene, pyridine, etc.). Therefore the molecular-orbital method is used much more often for the solution of wave equations.5 If we look at benzene by this method (qualitatively), we see that each carbon atom, being connected to three other atoms, uses sp1 orbitals to form a bonds, so that all 12 atoms are in one plane. Each carbon has a p orbital (containing one electron) remaining and each of these can overlap equally with the two adjacent p orbitals. This overlap of six orbitals (see Figure 2.1) produces six new orbitals, three of which (shown) are bonding. These three (called it orbitals) all occupy approximately the same space.6 One of the three is of lower energy than... 

Today our understanding is more sophisticated. Chungstun Chin 39) in this volume reviews the recent history of the structure-bonding-property guidelines which have been developed for NLO s over the past twenty years and concludes with a discussion of his recent work on borates so we will forego a further extended discussion of recent structure-property-bonding work in NLO s. Suffice to say our post facto explanations of NLO s are now vastly improved over what they were decades ago but in common with the theoretical situation in most of solid state chemistry our a priori prediction of which new systems to look at for improved properties is still rudimentary. 

Only fully saturated six-membered rings are really chairs or boats. Even with one double bond in the ring, the ring is partly flattened here we will look at ail even flatter example. A unique antibiotic has been discovered in China and called chuangxinmycin (meaning a new kind of mycin where mycin -antibiotic). It is unique because it is a sulfur-containing indole few natural products and no other antibiotics have this sort of structure. 

Why is the exo product the more stable Look again at these two structures. On the left-hand side of the molecules, there are two bridges across the ends of the new bonds (highlighted in black) a one-C-atom bridge and a two-C-atom bridge. There is less steric hindrance if the smaller (that is, the one-atom) bridge eclipses the anhydride ring. 

The representation of an EM corresponds to a chemist s way of looking at molecules. Therefore we have created a framework [36] for handling the dynamical data structures without comparison with reference systems. Many procedures that exist in C and Pascal e.g. create atom, create bond, delete bond facilitate handling. Thus, the creation of a new type of bond and the respective operator simply corresponds to a combination of some of these procedures. The generalization of the theory of the be- and r-matrices now comprises the... 

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