Metal d. pi. -ligand. pi. conflicts in octahedral oxo, carbyne, and carbonyl complexes
Metal-ligand ..pi.. interactions in group VI model compounds containing oxo, carbyne, and carbonyl ligands are probed with use of the extended Hueckel method. The interplay between M double bond O ..pi.. bonding optimization and the metal sigma framework geometry in (MoO/sub 2/H/sub 4/)/sup 2 -/ is examined first. The importance of oxygen's electronegativity for housing lone pairs in monomers containing terminal oxygens is noted and later contrasted with similar model compounds containing carbyne ligands. Calculations on (W(CH)/sub 2/H/sub 4/)/sup 4 -/ confirm the qualitative expectation that a nonbonding carbon 2p orbital combination exists for both cis and trans isomers. Even though this orbital is not at particularly high energy for a filled frontier orbital, they anticipate that these carbyne carbons will be vary nucleophilic if filled or very electrophilic if vacant; i.e., they will resemble a carbanion or a carbonium ion. A mixed oxocarbyne complex, such as (W(CH)(O)H/sub 4/)/sup 3 -/ will exhibit a d..pi.. conflict with the covalency requirements of the carbyne causing electron density to build up on the terminal oxygen. Competition for d..pi.. orbitals also results when ..pi..-acid ligands are trans to ..pi..-donor ligands. Recognition of ..pi..-acid/..pi..-donor d..pi.. conflicts rationalizes the cis geometry of W(O)(CO) in d/sup 2/ M(O)(CO)L/sub 4/ octahedra.
- Research Organization:
- Univ. of North Carolina, Chapel Hill
- OSTI ID:
- 6087040
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 109:17
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBONYLS
ELECTRONIC STRUCTURE
MOLECULAR MODELS
CARBYNES
LIGANDS
VANADIUM COMPLEXES
CHEMICAL BONDS
OXYGEN
THEORETICAL DATA
COMPLEXES
DATA
ELEMENTS
INFORMATION
MATHEMATICAL MODELS
NONMETALS
NUMERICAL DATA
RADICALS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties