CO substitution and diphosphine ligand chelation in the reaction between 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) and Re(2(CO)8(μ-H)(μ-η,η-C CPh)

The reaction between the redox-active diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) and the dirhenium compound Re₂(CO)₈(μ-H)(μ-η¹,η²-C CPh) in CH₂Cl₂ at room temperature proceeds by CO loss to give the dirhenium complex Re₂(CO)₇(bpcd)(μ-H)(η¹-C CPh) (1). This new complex was characterized in solution by IR and NMR (¹H and ³¹P) spectroscopy and in the solid state by X-ray diffraction analysis. Re₂(CO)₇(bpcd)(μ-H)(η¹-C CPh) crystallizes in the triclinic space group

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γ = 69.240(6)°, V = 2024.9(3) ų, Z = 2, d_calc = 1.862 g cm⁻³ R = 0.0221, R_w = 0.243 for 4066 observed reflections. The bpcd ligand in 1 adopts a chelating mode with a linear phenylacetylide ligand being located on the adjacent rhenium center cis to the bpcd ligand. This complex represents the first structurally characterized example of a hydrido-bridged dirhenium complex possessing both a linear acetylide ligand and a chelating diphosphine ligand.