After ensuring that Rh(II) metalloradicals, the catalytically active centers in hydrosilylation, can be quantitatively generated throughout the MOF framework, we studied the interaction between the Rh(II) center with reagents: Addition of diethylmethylsilane to a suspension of Rh(II)-3 gave rise to an immediate and drastic change in the appearance of the EPR spectrum, which was consistent with the formation of 3c-3e silane σ-adduct 6. The EPR signal of 6 is associated with substantially different g-values compared to Rh(II)-3, which can be rationalized based on the bonding interactions predicted by first principle quantum mechanical calculations of 6. The increase in the electron density at the Rh center brought about by σ-donation from the silane to the Rh center lifts the energy of the dz 2 orbital and thus increases the energy gap between the dz 2 and dxz/ dyz orbitals. Since