New reactivity patterns for abundant polar molecules such as water and ammonia in transition metal catalyzed organic reactions could greatly expedite synthetic chemistry. Our lab has been studying the use of phosphine ligands functionalized with heterocycles capable of accepting, donating, or in a rare case both, hydrogen bonds and protonation states with neighboring ligands. In particular, protic imidazolyl groups offer the unique ability to behave as both a hydrogen bond donor and acceptor, while maintaining a conserved steric profile and neutral charge. We have previously observed an imidazolyl phosphine platinum complex capable of N-H activation and stabilization of a rare example of a Pt-center ligated by a hydrido- and hydroxido-ligand simultaneously. Recently, we have found that by increasing the steric bulk on the imidazolyl group, a two-coordinate Pt (0) complex can be isolated. This bis-phosphine Pt (0) complex is capable of activating an O-H bond of water to yield a hydrido- / hydroxido-complex; analogous to the system studied previously. The imidazolyl group is also responsive to changing conditions. Addition of acid protonates the hydroxido-ligand, yielding a cationic aquo-complex in which the imidazolyl groups accept hydrogen bonds from the coordinated water. One feature of this system consistent in all NMR and X-Ray diffraction characterization is the trans coordination geometry of the phosphine ligands. We are currently using key features of these phosphine complexes to design new ligands that can enforce a cis-coordination geometry for the phosphine ligands, and also capable of similar hydrogen bonding interactions. A major thrust of this research is towards phosphine substituted ferrocenes. Results from reactivity studies with both the bulky trans complexes and the cis phosphine complexes will be discussed.

Studies on phosphine ligands containing protic imidazolyl groups for the activation of O-H bonds

2019 Fall National Meeting

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