Gold complexes containing redox-active ambiphilic P/Sb ligands: Synthesis, structure and catalytic properties
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abstract
With the support of the Chemical Synthesis Program of the Chemistry Division, Professor François Gabbaï of the Chemistry Department at Texas A&M University iinvestigates the chemistry of phosphine gold complexes that incorporate a Lewis acidic antimony atom as part of the ligand architecture. The goal of this project is to determine if the redox state of the antimony center can be used to modulate the Lewis acidity and catalytic properties of the gold center. This idea is being tested by investigating the catalytic properties of the complexes in the electrophilic activation of alkynes. Altogether, this research program helps to validate the notion that ligands combining a phosphine with an antimony center can be used for the construction of novel redox-responsive catalysts. In addition to contributing to the education of a diverse group of students, this project allows the principle investigator to maintain his involvement in various service and outreach activities involving K-6 students.A series of gold complexes featuring ambiphilic ligands containing phosphines as σ-donors and an antimony atom as a σ-acceptor are investigated with the ultimate goal of understanding whether the redox state of the antimony atom can be used to modulate the Lewis acidity and catalytic properties of the gold center. This idea is being tested by studying gold complexes featuring mono(phosphino)antimony and bis(phosphino)antimony ligands. For both type of complexes, oxidation of the antimony atom from the +III to the +V state is expected to activate the gold center and enhance its affinity for Lewis basic substrates including alkynes. The mono(phosphino)antimony derivatives is designed such that activation occurs by abstraction of a gold-bound halide ligand by the neighboring Lewis acidic antimony center. Activation of the complexes featuring a bis(phosphino)antimony ligand is expected to occur through formation of a direct Au→Sb interaction. For both families of complexes, the extent of activation experienced by the gold center is derived from an experimental determination of its Lewis acidity, as well as from its ability to catalyze reactions involving alkynes. At the heart of this project lies the fundamental notion that the redox state of antimony ligands can be manipulated as a means to adjust the reactivity of a transition metal center held in proximity by ancillary ligands. These fundamental advances may prove transformative in the area of redox-responsive ligands, with applications in sensing and catalysis. Another important outcome of this project is the involvement and education of a diverse group of students. The educational plan also includes outreach to students enrolled in Spanish/English K-6 dual language classes at local elementary and intermediate schools.
