High Oxidation State Rhodium and Iridium Bis(silyl)dihydride Complexes Supported by a Chelating Pyridyl-Pyrrolide Ligand

New rhodium and iridium complexes containing the bidentate ligand 3,5-diphenyl-2-(2-pyridyl)pyrrolide (PyPyr) were prepared. The bis(ethylene) complex (PyPyr)Rh(C2H4)2 (3) reacted with HSiEt3, HSiPh3, and HSitBuPh2 to produce the 16-electron Rh(V) bis(silyl)dihydrides (PyPyr)Rh(H)2(SiEt3)2 (8), (PyPyr)Rh(H)2(SiPh3)2 (9), and (PyPyr)Rh(H)2(SitBuPh2)2 (10), respectively. The analogous Ir(V) bis(silyl)dihyride (PyPyr)Ir(H)2(SiPh3)2 (11) has also been synthesized. X-ray crystallography reveals that 9−11 adopt a coordination geometry best described as a bicapped tetrahedron. Silane elimination from 9 and 10 occurred in the presence of either HSiEt3 or PPh3. Mechanistic studies of the silane exchange process involving 10 and free HSiEt3 (to give 8) indicate that this process occurs by rate-limiting reductive elimination of HSitBuPh2 from 10 to generate a 14-electron Rh(III) intermediate of the type (PyPyr)Rh(H)(SitBuPh2).