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

Dichloro(1,3-bis(diphenylphosphino)propane)nickel
Other names 1,3-bis(diphenylphosphino)propanenickel(II) chloride
Identifiers
CAS number	15629-92-2
Properties
Molecular formula	C27H26Cl2NiP2
Molar mass	542.04 g mol−1
Appearance	Orange to yellow orange powder
Melting point	213 °C, 486 K, 415 °F
Solubility in water	immiscible in water
Hazards
MSDS	[1]
R-phrases	R49-36/37/38-42/43
S-phrases	S53-26-36/37/39-45
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Infobox references

Dichloro[1,3-bis(diphenylphosphino)propane]nickel a coordination complex with the formula NiCl₂(dppp) (where dppp = Ph₂PCH₂CH₂CH₂PPh₂). It is used as a catalyst in organic synthesis. The compound is an orange crystalline powder.

Structure and properties

The compound exhibits C_2v symmetry with square planar geometry at the central nickel atom. The compound is soluble in non-polar organic solvents and is diamagnetic.

Preparation

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

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

Reactions

It is used in Grignard reagent reactions involving cross-coupling of aryl halides, converting enol ethers, dithioacetals, and vinyl sulfides to olefins. NiCl₂(dppp) is used because the douple phosphate ligand minimizes the reduction reactions with labile β-hydrogens.^[2]

Cross-coupling reactions of R-X compounds with organometallic nucleophiles are catalyzed by transition metal complexes such as NiCl₂(dppp). The R group consists of aryl, vinyl, or allyl groups and the X group is a good leaving group. Cross-coupling reactions are effective at producing carbon-carbon bonds. Catalysts that have bidentate phosphine ligands serve as the best catalysts.^[3]

NiCl₂(dppp) serves as the catalyst by bonding the two cross-coupling components to the nickel. The cross-coupling proceeds by oxidative addition of the aryl, vinyl, or allyl halide to NiCl₂(dppp) forming an oxidative addition adduct, R₁-NiCl(dppp). The organometallic nucleophile, R₂-MgBr, reacts with R₁-NiCl(dppp) and is followed by the cross-coupling reaction producing the R₁-R₂ product.^[4]

The compound is a catalyst for Kumada coupling reactions involving alkyl, alkenyl, aryl, and heteroaryl Grignard reagents with aryl, heteroaryl, and alkenyl halides.^[1]

References

1. ^ ^{a b} Kumada, Makota; Tamao, Kohei; Sumitani, Koji (1988), "Phosphine-Nickel Complex Catalyzed Cross-Coupling of Grignard Reagents with Aryl and Alkenyl Halides: 1,2-dibutylbenzene", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0407 ; Coll. Vol. 6: 407 
2. ^ Sigma-Aldrich. CAS 15629-92-2.
3. ^ Tien-Yau Luh; Tien-Min Yuan. ”Cross-Coupling Reactions”. Encyclopedia of Reagents for Organic Synthesis. DOI: 10.1002/047084289X.rd100.pub2.
4. ^ Ljungdahl, Thomas; Bennur, Timmanna; Dallas, Andrea; Emtenaes, Hans; Maartensson, Jerker (2008). "Two Competing Mechanisms for the Copper-Free Sonogashira Cross-Coupling Reaction". Organometallics 27 (11): 2490–2498. doi:10.1021/om800251s.