Synthesis and characterization of cationic rhodium complexes with stable silylenes

Two cationic rhodium(I)-tetrasilylene complexes, [Rh(SitBuNHC=CHNtBu)(4)]BArF (4; BArF tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) and [Rh(SitBuNH(2)C=CH(2)NtBu)(4)]BArF (5), were prepared from [Rh(cod)(2)]BArF and 1,3-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazasilol-2-ylidene (1) or its saturated analogue 2, respectively (Figure 1). The two complexes were characterized by X-ray analysis and NMR spectroscopy. The crystal structures revealed a square-planar coordination geometry for both complexes. Only tetrakis(silylene) complexes were formed, even in the presence of less than 4 equiv of silylene.