Cationic (η5-C5Me4R)RhIII Complexes with Metalated Aryl Phosphines Featuring η4-Phosphorus plus Pseudo-Allylic Coordination

In this contribution we study experimentally and computationally some electrophilic cationic (eta(5)-C5Me4R)Rh-III complexes containing a cyclometalated bis(aryl) phosphine, PR'Ar-2. The phosphine Ar groups feature methyl substituents at the 2- and 6-positions of the aromatic rings, allowing the formation of the complexes [(eta(5)-C5Me4R)Rh(C boolean AND P)](+) (3(+)), where the metalated phosphine exhibits eta(4) coordination to rhodium through phosphorus and the carbon atoms of the adjoining pseudo-allylic functionality. The solution and solid-state structures of complexes 3(+) have been studied by NMR and X-ray methods and their electronic properties investigated with the aid of DFT calculations. The Lewis acid behavior of complexes 3(+) has also been addressed, concentrating on reactivity toward CO, H-2,and hydrosilanes. Some catalytic Si-H/Si-D exchange and hydrosilylation reactions are also reported.