Coordination and C–H activation of an amidobis(phosphaalkene) ligand at rhodium(i)

Abstract

Phosphaalkenes are an underrepresented class of phosphorus-based ligands that hold great potential for the stabilisation of low-valent transition metal and main group fragments. We present the synthesis of a monoanionic PNP-type bis-phosphaalkene ligand and its reactions with [Rh(cod)(Cl)]₂, which furnish two unique dinuclear Rh(I) complexes. These complexes show C–H activation of the Mes* groups of the PNP ligand and the presence of three different phosphaalkene coordination modes, respectively. Computational analyses suggest the presence of a unique Rh–Rh donor–acceptor interaction in the C–H-activated complex. Stabilisation of the desired tricoordinate PNP-supported Rh(I) species is possible in the presence of the strongly donating CO ligand, yielding a mononuclear square-planar complex of the type [(PNP)Rh(CO)].