Synthesis, Structural Studies, And Redox Chemistry Of Bimetallic [Mn(Co)(3)] And [Re(Co)(3)] Complexes

Manganese ([Mn(CO)(3)]) and rhenium tricarbonyl ([Re(CO)(3)]) complexes represent a workhorse family of compounds with applications in a variety of fields. Here, the coordination, structural, and electrochemical properties of a family of mono- and bimetallic [Mn(CO)(3)] and [Re(CO)(3)] complexes are explored. In particular, a novel heterobimetallic complex featuring both [Mn(CO)(3)] and [Re(CO)(3)] units supported by 2,2 '-bipyrimidine (bpm) has been synthesized, structurally characterized, and compared to the analogous monomeric and homobimetallic complexes. To enable a comprehensive structural analysis for the series of complexes, we have carried out new single crystal X-ray diffraction studies of seven compounds: Re(CO)(3)Cl(bpm), anti-[{Re(CO3)Cl}(2)(bpm)], Mn(CO)(3)Br(bpz) (bpz = 2,2 '-bipyrazine), Mn(CO)(3)Br(bpm), syn- and anti-[{Mn(CO3)Br}(2)(bpm)], and syn-[Mn(CO3)Br(bpm)Re(CO)(3)Br]. Electrochemical studies reveal that the bimetallic complexes are reduced at much more positive potentials (Delta E >= 380 mV) compared to their monometallic analogues. This redox behavior is consistent with introduction of the second tricarbonyl unit which inductively withdraws electron density from the bridging, redox-active bpm ligand, resulting in more positive reduction potentials. [Re(CO3)Cl](2)(bpm) was reduced with cobaltocene; the electron paramagnetic resonance spectrum of the product exhibits an isotropic signal (near g = 2) characteristic of a ligand-centered bpm radical. Our findings highlight the facile synthesis as well as the structural characteristics and unique electrochemical behavior of this family of complexes.