Comparative Studies on the Electronic Structures of W2(O2CH)4 and W2(O2CH)4-(CH3)2 by the Relativistic X Alpha-SW Method: A d3-d3 Metal Dimer with a Quadruple Metal-Metal Bond?
INDIANA UNIV AT BLOOMINGTON DEPT OF CHEMISTRY
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The bonding in W2O2CR4 and in the recently characterized W2O2CR4R2 molecules are compared via Xalpha-SW calculations with quasi-relativistic corrections on the model system W2O2CH4 I and W2O2CH4CH32 II. Several questions concerning the electronic structure of II have been addressed in particular, the apparently strong W-W bond in the presence of strong W-C bonds was of interest. It has been found that II is best considered as a W2O2CH4 fragment interacting with two CH3 radicals, a description consistent with the photochemical decomposition of W2O2CEt4CH2Ph2. The resulting W-W bond still remains the essential components of the quadruple bond in I. The W-W bonding remains strong in spite of strong axial ligation because of involvement of a higher-lying s-s sigma bonding orbital, an orbital whose contribution is more important in II than in I. It is the presence of this orbital, which is lower-lying for third-row metals than for first, which is believed to account for the structural difference between CR2O2CR4L2 and the W2O2CR4R2 systems.
- Polymer Chemistry