27 In order to facilitate the visualization of dynamical processes such as mutual exchange in coordination complexes, electrocyclic reactions, and intramolecular DielsAlder reactions, we have developed a methodology for mapping an initial atomic configuration into a final one. The first step is to assure maximum coincidence of the (labeled) atoms in the initial and final arrangements. This is accomplished by requiring that the mass-weighted residual be at a minimum m'[R'(final) -Ri(initial)12where the Ri's are particle position vectors. It is generally convenient to operate in a center-of-mass coordinate system, though with simple coordination complexes it may be acceptable to place the origin at the central atom. The second step involves motion along some pathway leading from the initial to the final configuration. Least-motion pathways defined in Cartesian coordinates are generally unsuitable, giving physically unreasonable intermediate structures. Quasi-least-motion pathways may be mapped, either in spherical polar coordinates (suitable for simple coordination complexes) or in internal coordinates (the most general case). While these pathways will not in general correspond to the lowest energy route from starting material to products, they should represent qualitative approximations of the actual pathways.We have used the spherical polar model for the rearrangement mechanisms for the distal isomer of CrH,[P-(OCH,),],. The trimethyl phosphite ligands were replaced by points of equal mass displaced outward along the Cr-P bond direction to the center-of-mass for the phosphite group. 70948-62-8.A detailed theoretical study of a trinuclear eight-electron cluster with a distorted metal core, M O~S~C $~-, leads to some general conclusions about the role of different capping, bridging, and terminal ligands in determining the electronic and geometrical structure of trinuclear clusters of the early transition metals.

Abstract.Bis[/x-1,2-benzisothiazol-3(2H) 91cm -l, F(000)= 1148, T=294K, final R = 0.049 for 3275 unique observations. The molecule is composed of two trigonal-bipyramidally coordinated Cu atoms with four saccharin groups and four imidazole groups. However, the four C6H4CO502 N groups are not structurally identical, two of them are each coordinated to only one Cu atom through the N atom, while the other two saccharin groups act as bidentate bridging ligands for the two Cu atoms, forming a Cu n dimer containing an eight-membered ring.-

No abstract

No abstract

No abstract