Synthesis and Characterization of Novel 7-6-7 Ring-Based PCP Pincer Rhodium Complexes

A series of Rh-PCP pincer complexes ((PCP)-P-iPr)Rh(L) bearing a novel alkylaryl mixed 7-6-7 ring skeleton has been synthesized and fully characterized. The 7-6-7 ring skeleton in the hydrido-chloro and carbonyl species was found to assume the cis and trans conformations, respectively, in solid state as determined by single crystal X-ray diffraction analysis. This suggested a flexibility of the backbone compared with the similar but strictly fixed anthracene backbone. Electron density on the central rhodium atom was investigated by IR experiments and by DFT computations. NMR monitoring of the reaction of the hydrido-chloro complex with base followed by application of H-2 showed the presence of what are likely to be the active 14e species and the dihydride derivative. Especially, noteworthy is the former that was found to be relatively stable, in contrast to the corresponding iridium complex. [Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon for the following free supplemental files: Additional text, tables, and figures.]