Dichloro(1,3-bis(diphenylphosphino)propane)nickel explained

Dichloro[1,3-bis(diphenylphosphino)propane]nickel a coordination complex with the formula NiCl₂(dppp); where dppp is the diphosphine 1,3-bis(diphenylphosphino)propane. It is used as a catalyst in organic synthesis. The compound is a bright orange-red crystalline powder.

Structure and properties

While the electronic and solid-state structure of the chloride congener is not known (due to low solubility in common analytical solvents), several studies have been carried out on the bromo and iodo derivatives.^[1] The complexes display a temperature-dependent interconversion between square-planar and tetrahedral geometries (diamagnetic and paramagnetic) in polar organic solvents (Keq between 1-3.68, depending on the solvent and temperature). In contrast, dichloro(1,2-bis(diphenylphosphino)ethane)nickel adopts a static square-planar (diamagnetic) structure in solution.

Preparation

NiCl₂(dppp) is prepared by combining equal molar portions of nickel(II) chloride hexahydrate with 1,3-bis(diphenylphosphino)propane in 2-propanol.^[2]

Ni(H₂O)₆Cl₂ + dppp → NiCl₂(dppp) + 6 H₂O

Reactions

NiCl₂(dppp) in an effective catalyst for coupling reactions such as the Kumada coupling^[2] and Suzuki reactions (example below).^[3] It also catalyzes other reactions that convert enol ethers, dithioacetals, and vinyl sulfides to olefins.^{[4] [5]}

Notes and References

1. Van Hecke . Gerald R. . Horrocks, Jr. . William DeW. . Ditertiary Phosphine Complexes of Nickel. Spectral, Magnetic, and Proton Resonance Studies. A Planar-Tetrahedral Equilibrium . Inorganic Chemistry . 1966 . 5 . 11 . 1968–1974 . 10.1021/ic50045a029.
2. Kumada. Makota. Tamao. Kohei. Sumitani. Koji . Phosphine-Nickel Complex Catalyzed Cross-Coupling of Grignard Reagents with Aryl and Alkenyl Halides: 1,2-Dibutylbenzene . 58 . 127 . 1978 . 10.15227/orgsyn.058.0127. Org. Synth..
3. Zhao. Yu-Long. Li, You . Li, Shui-Ming . Zhou, Yi-Guo . Sun, Feng-Yi . Gao, Lian-Xun . Han, Fu-She . A Highly Practical and Reliable Nickel Catalyst for Suzuki-Miyaura Coupling of Aryl Halides. Advanced Synthesis & Catalysis. 1 June 2011. 353. 9. 1543–1550. 10.1002/adsc.201100101.
4. Tien-Yau Luh; Tien-Min Yuan. "Cross-Coupling Reactions". Encyclopedia of Reagents for Organic Synthesis .
5. Ljungdahl, Thomas . Bennur, Timmanna . Dallas, Andrea . Emtenaes, Hans . Maartensson, Jerker . Two Competing Mechanisms for the Copper-Free Sonogashira Cross-Coupling Reaction . . 27 . 11 . 2490–2498 . 2008 . 10.1021/om800251s.