The Rohde Group synthesizes and investigates reactive transition metal complexes to develop new methods for the activation of small molecules and catalytic functionalization of organic compounds. Specific synthetic targets include i) organometallic complexes that mediate small-molecule activation chemistry, ii) complexes of late transition metals in high oxidation states, and iii) complexes of redox-active ligands.

Activation of Small Molecules by Metal–Alkene Complexes
Molecular oxygen is a much desired oxidant for the functionalization of organic compounds, as it is readily available and inexpensive. The development of selective methods, however, remains a challenging task. In this context, organometallic O2 reactivity is an area of growing interest, because it offers insights into possible oxygenation mechanisms and provides a basis for the design and development of new catalytic methods. We have been investigating the activation of O2 and other small molecules by low-valent Ir alkene complexes. This work has led to the identification of (alkene)peroxo intermediates, where both the oxidant and the substrate are bound to the metal center. Such species are intriguing, because they have been proposed as key intermediates in stoichiometric and catalytic alkene oxygenation.

High-Oxidation State Complexes of Late Transition Metals
Complexes of late transition metals in high oxidation states are attractive synthetic targets, because they often are proposed as intermediates in C–H bond activation, oxygen atom transfer, and water oxidation chemistry. In our research, the use of strongly donating guanidinato ligands has led to the discovery of a new class of IrIV complexes. These complexes are sufficiently stable to be characterized by spectroscopic and crystallographic methods. Our current efforts are focused on the stabilization of other transition metals in high oxidation states as well as the reactivity of these complexes toward organic substrates.

Synthesis, Structure and Reactivity of Complexes of Redox-Active Ligands
Due to their capacity to participate in the multielectron redox chemistry of a coordinated metal center, redox-active ligands can facilitate bond-forming and bond-breaking processes. Our research in this area is focused on the synthesis of ligand-radical complexes of Co and Ni, the elucidation of their molecular and electronic structure through spectroscopic and crystallographic studies, and their reactivity toward small molecules such as O2.