Transition-metal complexes bearing outer-sphere pendent bases show enhanced acceptorless dehydrogenation (ADH) catalysis rates (relative to analogs without pendent bases) as a result of Metal-Ligand cooperativity. Our group is interested in contributing to the limited number of studies that focus on exploring how proton affinity and basicity of pendent bases impacts overall catalytic performance. In this poster, we will discuss our efforts to synthesize and characterize two new BIPHEP-type ligands. A non-functionalized BIPHEP derivative, 2,2'-bis(di(2-ethylphenyl)phosphino)biphenyl, has been prepared by a four-step synthesis involving a final Cu-catalyzed Ar-Ar cross-coupling step. A carboxylic acid-functionalized BIPHEP derivative, 2,2'-bis(di(2-COOH-phenyl)phosphino)biphenyl, has been prepared by a different four-step synthesis involving a penultimate Pd-catalyzed Ar-P cross-coupling step. We have used 4,4-dimethyl-2-phenyl-2-oxazolyl protecting groups to protect the carboxylic acid functionalities from reacting under the basic and reducing conditions used during the synthesis route. The functionalized ligand will be converted to other ligands with various pendent bases such as amides, alcohols, and amines. We will also discuss the synthesis and characterization of Ru(II) complexes bearing prepared ligands as well as our initial results from optimizing the conditions for ADH catalysis.

Synthesis, characterization, and catalytic acceptorless dehydrogenation performance of Ru(II) complexes bearing BIPHEP-type ligands

ACS Spring 2022

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