Triple-decker complex CpCo(μ-C3B2Me5)Rh(C2H4)2: Synthesis, structure and bonding

• The title compound 4 was synthesized with high yield.
• Triple-decker complex 4 was structurally characterized.
• The calculated Rh–C2H4 bonding in 4 is 10 kcal mol−1 weaker compared to CpRh(C2H4)2.

The reaction of the thallium derivative [CpCo(μ-C3B2Me5)]Tl with [Rh(C2H4)2Cl]2 affords the μ-diborolyl bis(ethylene) triple-decker complex CpCo(μ-C3B2Me5)Rh(C2H4)2 (4). Structure of 4 was determined by X-ray diffraction. According to DFT calculations, the ethylene dissociation energies for the triple-decker complexes CpCo(μ-C3B2R5)Rh(C2H4)2 (R = H, Me) are ca. 6 kcal mol−1 lower than for cyclopentadienyl analogs (C5R5)Rh(C2H4)2. Energy decomposition analysis revealed that the bonding of anions [CpCo(C3B2R5)]− with [Rh(C2H4)2]+ is also weaker than that of [C5R5]−; the attractive interactions in both cases are 60–63% electrostatic and 37–40% covalent. The electrostatic potentials at the Rh nuclei suggest that the donor ability of the anions increases in the following order: Cp < [CpCo(C3B2H5)] ⩽ [CpCo(C3B2Me5)] < Cp∗.

The triple-decker complex CpCo(µ-C3B2Me5)Rh(C2H4)2 (4) was synthesized with high yield and structurally characterized. DFT calculation shows that Rh–C2H4 bonding in 4 is 10 kcal mol–1 weaker compared to CpRh(C2H4)2.Figure optionsDownload as PowerPoint slide