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44644-AC3
A New Twist on Pincer Complexes for Catalysis

John Protasiewicz, Case Western Reserve University

During the second and final funding period of this award, we continued to examine metal-ligand complexes that bear the new pincer ligands (Chart 1).  In this report we can now claim that we have developed representatives of all of the ligand precursors shown in Chart 1. 

Chart 1.

  We have furthermore shown that each type of system can be used to prepare palladium pincer complexes (Scheme 1).

Scheme 1.

Two papers were published having different metal complexes in the first funding period.  To these we can add two more papers that have been published or are in press.  In a JOMC report we detail the synthesis and characterization of nickel and palladium complexes of diammine ligands 2e.  The catalytic potential of diphosphine and diphosphinite complexes have been examined as catalyst precursors for the Suzuki-Miyaura coupling of aryl halides with aryl boronic acids (Scheme 2).

Scheme 2.

In unpublished work, we have succeeded in obtaining a novel structure of ligand 2h (Figure 1). 

The project has contributed to the development and education of several graduate and undergraduate students as follows: Graduate students Robert Woloszynek (Senior Scientist, Goodyear) and Liqing Ma (Postdoctoral Associate, University of North Carolina, Chapel Hill); Undergraduate students: Mark Lipke (PhD Candidate, University of California, Berkeley), Catherine Smith (current undergraduate researcher), and Andrew Long (current undergraduate researcher).