![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
Flexible, linear, tetranuclear palladium complexes supported by tetraphosphine ligands with electron-withdrawing
Tomoaki Tanase1, Satoko Hatada, Ayaka Mochizuki
1Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoya-nishi-machi, Nara 630-8506, Japan. tanase@cc.nara-wu.ac.jp.
Dalton Transactions (Cambridge, England : 2003)
|July 25, 2013
Summary
A new tetraphosphine ligand, dpmppmF2, effectively organizes dynamically flexible tetrapalladium chains. These complexes exhibit fluxional behavior in solution, transitioning between asymmetric and symmetric structures depending on temperature.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Materials Science
Background:
- Tetranuclear palladium complexes offer unique structural and electronic properties.
- Tetraphosphine ligands are crucial for stabilizing polynuclear metal clusters.
- Electron-withdrawing groups on ligands can influence metal center reactivity and complex stability.
Purpose of the Study:
- To synthesize and characterize novel tetranuclear palladium complexes supported by a new tetraphosphine ligand.
- To investigate the structural dynamics and electronic properties of these complexes in solution and solid states.
- To explore the role of the tetraphosphine ligand in organizing palladium chains.
Main Methods:
- Synthesis of meso-bis[{di(3,5-difluorophenyl)phosphinomethyl}phenylphosphino]methane (dpmppmF2) ligand.
- Reaction of dpmppmF2 with palladium precursors ([Pd2(RNC)6](PF6)2 and Pd(dba)2) to form tetranuclear complexes.
- Variable-temperature UV-vis and NMR spectroscopy ((31)P{(1)H}, (1)H) for structural and dynamic studies.
- Density Functional Theory (DFT) calculations to elucidate electronic structures and bonding.
Main Results:
- Formation of asymmetric tetranuclear palladium complexes [Pd4(μ-dpmppmF2)2(RNC)3](PF6)2 with a unique {(RNC)Pd4(CNR)2}(2+) core.
- Identification of a dipalladium(I) complex as a key intermediate in the formation mechanism.
- Observation of temperature-dependent fluxional behavior in solution, with a transition from asymmetric to symmetric structures.
- DFT calculations suggest dominant Pd(0)→Pd(I)-Pd(0)-Pd(I) (60 CVEs) for asymmetric and Pd(I)-Pd(0)-Pd(0)-Pd(I) (58 CVEs) for symmetric structures.
Conclusions:
- The dpmppmF2 ligand is highly effective in organizing dynamically flexible tetrapalladium chains.
- The electronic properties and fluxional behavior of the complexes are influenced by the ligand's electron-withdrawing groups and temperature.
- The study provides insights into the structural diversity and dynamic nature of polynuclear palladium complexes.
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