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High-Valent Transition-Metal Alkylidene Complexes: Effect of Ligand and Substituent Modification


Article on high-valent transition-metal alkylidene complexes and the effect of ligand and substituent modification.

Creation Date: 1992
UNT College of Arts and Sciences
UNT Scholarly Works
Total Uses: 284
Past 30 days: 5
Yesterday: 2
Creator (Author):
Cundari, Thomas R., 1964-

University of North Texas; North Dakota State University

Creator (Author):
Gordon, Mark S.

North Dakota State University

Publisher Info:
Publisher Name: American Chemical Society
Place of Publication: [Washington, DC]
  • Creation: 1992

Article on high-valent transition-metal alkylidene complexes and the effect of ligand and substituent modification.

Department: Chemistry

Reprinted with permission from the Journal of the American Chemical Society. Copyright 1992 American Chemical Society.


Abstract: An ab initio investigation into the effects of ligand and substituent modification on the metal-carbon double bond is reported. Prototypical group IVB (Ti, Zr, Hf) and Group VB (Nb, Ta) alkylidenes are chosen for this study. The MC/LMO/CI (multiconfiguration/localized molecular orbital/configuration interaction) procedure is used to examine the electronic structures of these complexes in terms of the prime resonance contributors to the ground-state wave function. The main conclusion drawn from this work is that the intrinsic nature of the metal-carbon double bond can typically be changed only within certain limits by modification of the electronegativity of the ligands (L) and substituents (Z). In other words, the Ta=C bond in H₃TaCCl₂ and Cl₃TaCH₂ and presumably in experimentally characterized analogues with larger ligands and substituents, e.g., Cp and neopentyl. Significant changes in the electronic structure are effected in three ways: The first way is through the introduction of a highly electropositive substituent, e.g., Li. This makes the metal-carbon bond closer to a triple bond for the Ta-alkylidenes. The second way to change the electronic structure of the alkylidenes significantly is to change the central metal atom. The heaviest members of groups IVB (Hf) and VB (Ta) are the most nucleophilic at the α-carbon. The third way in which the metal-carbon bond could be significantly altered is through the use of π-donor substituents. The introduction of π-donor substituents on Cα increases the electrophilicity of the α-carbon.

Physical Description:

10 p.

Keyword(s): transition metals | alkylidene complexes | ligands | substituents
Source: Journal of the American Chemical Society, 1992, Washington DC: American Chemical Society, pp. 539-548
UNT College of Arts and Sciences
UNT Scholarly Works
  • DOI: 10.1021/ja00028a022 |
  • ARK: ark:/67531/metadc107774
Resource Type: Article
Format: Text
Access: Public
Publication Title: Journal of the American Chemical Society
Volume: 114
Issue: 2
Page Start: 539
Page End: 548
Peer Reviewed: Yes