4-Ethynylpyridine as a bridging moiety in mixed Rh/Re complexes

A paramagnetic, dimeric RhIIIRhII complex of the formula [Rh2(form)4(C≡CC5H4N)] (1) [form = N,N′-di-p-tolylformamidinate; C5H4N = pyridyl (py)] has been synthesized and used as starting material to prepare heterotrimetallic complexes of composition [Rh2(form)4(C≡Cpy){Re(CO)3(bipy)}][OS(=O)2CF3] (2) and [Rh2(form)4(C≡Cpy){Re(CO)3(tbu2bipy)}][OS(=O)2CF3] (3). These complexes have been examined by vibrational spectroscopy, EPR spectroscopy, thermogravimetry and cyclic voltammetry. They are heat-stable and can be handled in air without problems. The observed interactions between the Rh2 and the Re subunits, however, are weak, and a significant charge transfer does not seem to take place.