The document discusses the regioselective C-H/C-X activation of naphthyl-derived ligands to form rare six-membered palladacycles using palladium(II) complexes with N^N^C pincer ligands. The palladium complexes were characterized using NMR spectroscopy and were found to selectively form six-membered rings over the more common five-membered rings. Future work is proposed to include different aromatic ligands and synthesize palladium(IV) complexes while conducting kinetic studies.

1. The Palladium(II) complexes were also characterized using 1
H NMR, 13
C NMR,
NOESY NMR, and HSQC NMR. The 1
H NMR spectra below illustrates the final
Palladium complexes without trace intermediates. The rare six-membered palladacycles
involving C-H/C-X activation were favored over the more common five-membered
palladacyles in high yield. Both methods of syntheses to form the six-membered
palladacyles involving Palladium(II) Acetate and Pd(dba)2
produced similar NMR
spectra, supporting the formation of stable six-membered metalacycles.
Palladium(II) complexes using N^N^C pincer ligands were successfully synthesized and
characterized. It is also noticeable that the complexes all demonstrated a certain degree of
regioselectivity in their synthesis. C-X bonds to form 6-membered rings were selectively
favored over the more frequently observed 5-membered palladacycles. In addition sp2
C-H
bonds were selectively activated over sp3
C-H bonds.
Future Work:
•Include ligands with thiophene and phenanthrene aromaticity.
•Successfully synthesize Pd(IV) complexes.
•Running kinetic studies of the formation of the complexes.
•Synthesizing other chelated and pincer-type ligand complexes.
UV-VIS & EMISSIONS
CONCLUSION & FUTURE WORK
Regioselective C-H/C-X Activation of Naphthyl-Derived Ligands
to form Six-Membered Palladacycles
Nathaniel Oh, Tedros A. Balema, Francesco Mastrocinque, Claudio Mastrocinque, Danielle Santos,
Matthew W. Greenburg, Joseph Tanski, and Craig M. Anderson.*
Chemistry Departments: Bard College, Annandale-on-Hudson, NY; Vassar College, Poughkeepsie, NY
This material is based upon work supported by the National Science Foundation under CHE–1058936 (Craig M. Anderson, P.I.)
INTRODUCTION DISCUSSION
C-H activation is an important area of research and the subject of much recent
work in several areas of chemistry, including organometallic chemistry, catalytic
chemistry, and bioinorganic chemistry. Selective C-H bond activation is a
potentially valuable approach to synthetic problems in areas ranging from fuels to
bulk chemicals and pharmaceutical synthesis. However, C-H bonds are generally
inert. Palladium pincer ligands were explored in order to observe competing C-H
and C-X activation. Traditionally, metalacycles are five-membered rings as these
form preferretially. However, rarer six-member palladacycles have been formed
using various pincer ligands involving C-H activation of sp2
-hybridized carbons
and C-X activation through electronegative leaving groups. These complexes have
been characterized using various methods and our results have recently been
published in the Tetrahedron Letters science journal.
The Palladium complexes were characterized using Low Temperature Emissions
(77 K) and UV-Vis. At low temperature (77 K) all four compounds had emission
spectra with very similar set of peaks between 600 and 607 nm with a shoulder
between 655 and 665 nm.