Inorganic
Honors: Pincer
Chemistry
Rajiv K. and Mark B.
Pincer Chemistry
• Pincer chemistry is utilized to facilitate interactions
between specific atoms
• Variety of pincer compounds exist and have several
purposes
Guan, H., Chakraborty, S., 2010, First-row transition metal catalyzed reduction of carbonyl functionalities: a
mechanistic perspective, Dalton Transactions, 39, 7427-7436.
Generation of the Pincer
Moiety
Positioning For
Metallation
Zargarian, D., Vabre, B., Lambert, M., Petit, A., Ess, D., 2012, Nickelation of PCP- and POCOPType Pincer Ligands: Kinetics and Mechanism, Organometallics, 31, 6041-6053.
Previous Work
• Previous students in the course performed the
following reaction:
• The following product was obtained:
Research Goals
• Develop a different stoichiometric scheme to
increase the yield of the unpredicted product
• Investigate the effects of the order of reagent
addition
Bimetallation
• Use of Pincer Chemistry to facilitate the formation of a
metal-metal bond
• X-Ray Crystallography to determine the product’s
structure
One Pot Synthesis
• Synthesis of compound performed under
inert atmosphere
• NMR of crude product taken
• Ran resulting compound through a column,
followed by NMR of bands
One Pot Synthesis
• Refluxed for 24 hours
One Pot Synthesis
• Oily mixture with green
metallic coating obtained
Summary
Crude
• P-NMR: 6 peaks, 180.64 ppm, 179.96 ppm,
178.82 ppm, 177.80 ppm, 173.78 ppm
Band 1
• Yield: 147.9 mg
• P-NMR: 4 peaks, 179.31 ppm and 178.37
ppm
Band 2
• Yield: 202.4 mg
• P-NMR: 3 peaks, 179.09 ppm, 178.92 ppm,
178.16 ppm
X-Ray Crystallography
Synthesis of Compound
Without Base
• Control reaction
• NMR taken after 24 hour reflux
• Refluxed for 48 hours total, then filtered
• Celite filtration
performed to
remove ionic
impurities
Two Step Approach: Slow
Resorcinol Addition
• Ligand synthesis and subsequent metallation were
performed under an inert atmosphere
• Ligand synthesis was monitored via P-NMR
Slow Resorcinol Addition: Monitoring Synthesis of Ligand
Slow Resorcinol Addition: Monitoring Synthesis of Ligand
Slow Resorcinol Addition: Monitoring Synthesis of Ligand
Slow Resorcinol Addition: Monitoring Synthesis of Ligand
Slow Resorcinol Addition: Crude Metallation Product
Slow Resorcinol Addition: Purification, 1st Band
Summary
Band 1
• Yield: 48.7 mg
• P-NMR: 2 Peaks, 155.83 ppm & 155.52
ppm
Band 2
• Yield: 59.4 mg
Band 3
• Yield: 30.2 mg
Two Step Approach: Slow
Phosphine Addition
• Ligand synthesis by the slow addition of phosphine
followed by metallation
• Results analyzed by P-NMR and H-NMR
Slow Phosphine Addition: Crude Ligand Product P-NMR
Slow Phosphine Addition: Isolation of Ligand P-NMR
Slow Phosphine Addition: Isolation of Ligand H-NMR
Slow Phosphine Addition– Metallation of Ligand P-NMR
Slow Phosphine Addition: Metallation of Ligand H-NMR
Growing crystals of 1,1′Bis(diphenylphosphino)ferro
cene (dppf)NiCl2
• Dative Fe-Ni bond
Growing crystals of 1,1′Bis(diphenylphosphino)ferro
cene (dppf)NiCl2
•
•
•
•
Ran reaction for 3 hrs using DCM as solvent
After evaporation, add 1:1 ratio of DCM then ether
Yield: 217 mg
Crystals have not been obtained
Conclusion
• Used pincer chemistry to facilitate metal-metal and
carbon-metal interactions
• Attempted several synthetic routes to obtain the
unpredicted product (Project 1)
o Methods included varying the stoichiometric scheme and the method of
reagent addition
• Attempted to crystallize the metal-metal interaction
complex for structural determination (Project 2)