Pyridine Functionalized N-Heterocyclic Silane Complexes of Iridium and Rhodium-An Unexpected Change in Coordination

A new pyridine functionalized N-heterocyclic silane with ambident reactivity as a ligand has been synthesized and characterized by NMR spectroscopy (¹H, ¹³C{¹H}, ²⁹Si), mass spectrometry, elemental analysis, and X-ray crystallography. This ligand reacts with iridium and rhodium cod precursors (cod = 1,5-cyclooctadiene) to yield two new complexes that possess divergent, and unexpected, binding properties. In particular, no oxidative addition occurs at the intraligand Si-H unit. With the iridium(I) center, the ligand acts as a tertiary amino-pyridine chelator, whereas coordination of rhodium(I) to the ligand occurs with arene π-complexation on an opposite side. The latter interaction yields an unprecedented, electronically induced, coordination change at the silicon center over a long spatial distance. The new iridium and rhodium compounds are of high interest as they provide two potentially different reactions sites in one complex and as these sorts of complexes are known to activate small molecules like dihydrogen or silanes. Hence, the compounds are promising candidates for applications in tandem catalysis. Furthermore, the rhodium complex might be utilized for molecular switches, sensors, and comparable applications.