Reactivity of Rhodium (II) and Irridium (II) olefin complexes in activation of dioxygen and other substrates

We have recently found that transient paramagnetic Ir(II) and Rh(II) species are essential intermediates in C-O bond making and O-O bond breaking upon reaction of dioxygen with N- ligand Ir(I)- and Rh(I)-olefin complexes. In an attempt to understand their role, we have recently prepared the first example of a stable and well-characterised Ir(II)-ethene complex and have initially investigated its reactivity towards O2. The reactivity towards O2, and DFT calculations, show that the coordinated ethene fragment has substantial radical character. Thus activation of the olefinic C=C double bond by the Ir(II) centre appears to be intermediate between free radical activation and transition metal coordination. This should allow us to break new ground in (catalytic) formation of C-C, C-O and C-N bonds from olefinic double bonds. We propose to synthesise a variety of new, stable Rh(II)- and Ir(II)-mono-olefin and diene complexes from their Rh(I)- and Ir(I) precursors. Our choice of the appropriate precursors will be guided by the electrochemical reversibility of their one-electron oxidation. Obtained species will be structurally characterised by EPR/ENDOR, UV-Vis, IR, 193Ir Mössbauer, paramagnetic NMR, and X-ray diffraction. The obtained Rh(II)- and Ir(II)-mono-olefin and diene species will be investigated for their reactivity towards: - O2, singlet O2 analogue triazolinedion, and radicals O2-,NO, TEMPO and semiquinone. - Olefins, CO, alkynes and conjugated dienes and enones. - Ethylene oxide and other epoxides. Financial support is requested for the appointment of a Ph.D.-student (OIO) at KUN, for small equipment, and for a benchfee covering costs of chemicals, travel and information retrieval.