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Updated: Jul 5, 2026
10:51
The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Electronic and steric effects in gold(i) phosphine thiolate complexes
J Foley1, R C Fort, K McDougal
1Department of Chemistry University of Maine Orono ME 04469-5706 USA.
Metal-Based Drugs
|January 1, 1994
Summary
Steric bulk in dinuclear gold(I) complexes influences gold-gold interactions and color. Bulky thiolates prevent gold atom proximity, resulting in white complexes, while less hindered thiolates allow closer approach and yellow coloration.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Dinuclear gold(I) complexes with diphosphine and thiolate ligands exhibit unique properties.
- The color of these complexes is linked to electronic transitions, specifically S-->Au charge transfer.
- Structural factors, such as ligand steric bulk, are hypothesized to influence gold-gold interactions and complex properties.
Purpose of the Study:
- To investigate the relationship between ligand structure, gold-gold proximity, and the observed color of dinuclear gold(I) complexes.
- To elucidate the electronic and steric factors governing the S-->Au charge transfer and its impact on spectral properties.
- To explore the conformational dynamics and potential for gold-gold bonding in these systems.
Main Methods:
- Synthesis of a series of dinuclear gold(I) complexes with varying thiolate ligands (R = 4-tolyl, 2,6-dichlorophenyl, 2,6-dimethylphenyl, 3,5-dimethylphenyl) and fixed diphosphine ligands (dppm, dppe).
- Variable temperature (VT) 31P{(1)H} NMR spectroscopy to study ligand exchange and conformational dynamics.
- UV-Vis spectroscopy to analyze electronic transitions and color.
- Molecular mechanics calculations to determine conformational preferences and energy barriers.
Main Results:
- The yellow color of Au(2)(dppm)(SR)(2) (R = 4-tolyl) is attributed to a red-shifted S-->Au charge transfer due to destabilization of the sulfur HOMO.
- VT-NMR revealed distinct dynamic behavior for Au(2)(dppm)(SR)(2) (two bands, 10 kcal/mol activation energy) compared to Au(2)(dppe)(SR)(2) (one band).
- Computational studies indicated that bulky 2,6-disubstituted thiolates lead to white complexes by hindering gold-gold approach, while the 3,5-dimethylphenyl derivative results in a yellow complex.
Conclusions:
- Steric bulk of the thiolate ligand is a critical determinant of gold-gold proximity in dinuclear gold(I) complexes.
- Hindered gold-gold approach, enforced by bulky thiolates, correlates with white coloration, suggesting suppressed S-->Au charge transfer.
- The conformational flexibility and electronic properties are intricately linked to the steric environment created by the ancillary ligands.
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