Catalytic decarbonylation of aldehydes using iron(II) porphyrin complexes, and the crystal structure of (5,10,15,20-tetraphenylporphinato)bis(tri-n-butylphosphine)iron(II)
The complex (5, 10, 15, 20-tetraphenylporphinato)bis(tri-n-butylphosphine)iron(II), 1, has been isolated in a triclinic crystal form, a = 12.499(3), b = 12.528(2), c = 12.039(2) Å, α = 116.39(1), β = 109.79(1), γ = 98.13(1)°, Z = 1, space group [Formula: see text]. The structure was solved by conventional heavy atom methods and was refined by full-matrix least-squares procedures to R = 0.060 and Rw = 0.070 for 3551 reflections with I ≥ 3σ(I). The molecule, which has crystallographic [Formula: see text], symmetry, displays a relatively undistorted pseudo-octahedral coordination geometry with Fe—P = 2.346(1) and Fe—N = 1.998(3) and 1.993(3) Å. In CH2Cl2 solution, 1 reacts with CO and aldehydes to generate the carbonyl(phosphine) derivative, and decarbonylation of phenylacetaldehyde to toluene becomes catalytic under an Ar stream. The aldehyde decarbonylations involve radical pathways via carbonyl loss from [Formula: see text]. The hydrogen abstraction/initiation reaction probably utilizes trace O2 (and possibly trace (water); speculative mechanisms are discussed.