Rhodium‐Mediated Dehydrogenation of Hydroboranes and Group 14 Compounds: Base‐Stabilized Silylene and Germylene Complexes vs. Transmetalation

Abstract

AbstractMonocarbonyl rhodium complex LRh(CO), 1, which is stabilized by a pyrrole‐based bis(phosphinimine) pincer ligand (L=κ3‐NNN’=2,5‐[iPr2P=N(4‐iPrC6H4)]2‐N’(C4H2)−), serves as a versatile platform for the dehydrogenation of group 14 substrates. Reaction with primary and secondary silanes and germanes (MesSiH3, Et2SiH2, Ph2GeH2, tBuGeH3; Mes=mesityl) liberates H2 and yields base‐stabilized tetrylene compounds of the form κ2‐L(CO)Rh(ER2) (E=Si: R=Mes, H, 2; R=Et, 5; E=Ge: R=Ph, 6; R=tBu, H, 8). The “:ER2” fragment in these species bridges between the rhodium center and a phosphinimine donor. Preliminary reactions between pinacol (Pin) and κ2‐L(CO)Rh(ER2), E=Si, Ge, indicate that such complexes can serve as silylene and germylene synthons, releasing :ER2 and catalytically generating PinER2. In contrast, combination of complex 1 and MesGeH3 does not yield the anticipated dehydrogenation product, but rather, transmetalation similar to that observed upon reaction between 1 and 3,5‐dimethylphenylborane prevails.