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)

Abstract

The complex (5,10,15,20-tetraphenylporphinato)bis(tri-n-butylphosphine)iron(II), 1, has been isolated in a triclinic crysgl form, a = 12.499(3), b = 12.528(2), c = 12.039(2) A, u = 116.39(1), P = 109.79(1), y = 98.13(1)", Z = 1, spacegroup P1.The structure was solved by conventional heavy atom methods and was refined by full-matrix least-squares procedures to R = 0.060 and R,, = 0.070 for 3551 reflections with I ? 3 u(l). The molecule, which has crystallographic 1-Ci 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) A.In CH2C1, 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 PhCH2C0. The hydrogen abstraction/initiation reaction probably utilizes trace O2 (and possibly trace (water); speculative mechanisms are discussed. [Traduit par la revue] Introduction Carbonylation reactions provide key steps in a range of homogeneously catalyzed processes of industrial importance (1, 2). Decarbonylation (for example, of aldehydes: RCHO +

Structural, 103Rh NMR and DFT Studies of a Bis(phosphane)RhIII–Porphyrin Derivative

“…Finally, we note the marked 3.738 ppm ring current-induced shielding for the ortho protons of the axial ligand aryl groups as a result of their spatial projection towards the central core of the Rh III porphyrin (the o-H signal shifts from δ = 7.484 to 3.746 ppm upon coordination of PEtPh 2 to [Rh(TPP)] + in the present solvent system). Similar porphyrin ring current induced shieldings are known for other low-spin d 6 metalloporphyrins. [31,32] From the 1 H NMR spectra of 1 above 253 K ( Figure S4), the axial ligands and meso-phenyl groups are in the fast exchange limit on the 500 MHz NMR timescale.…”

“…Returning to the aquation adduct [Rh(TPP)(OH 2 )-(PEtPh 2 )]SbF 6 , we found that the extent of equilibration to the monoaqua complex could be reduced, but not completely eliminated, by first passing the CDCl 3 used for solution preparation through a short column of activated alumina. This problem unfortunately persisted even when using clean crystalline material with good elemental analysis data for solution preparation.…”

“…Indeed, addition of water-saturated dichloromethane to a solution of 1 in dry dichloromethane afforded a small saturating fraction of [Rh(TPP)(OH 2 )-(PEtPh 2 )]SbF 6 with an increase in the water content of the solution, as evidenced by the appearance of the B and Q bands at ca. 420 and 527 nm, respectively, bands that are characteristic of this species ( Figure S1, Supporting Information).…”

“…420 and 527 nm, respectively, bands that are characteristic of this species ( Figure S1, Supporting Information). 6 was characterised by the loss of the Soret band intensity at 448 nm, with concomitant appearance of a new Soret band for the mixed-ligand solvolysis product at 425 nm.…”

“…diphenyl(2-phenylethynyl)phosphane]. [5] Structures of the isoelectronic low-spin Fe [6] are also known, not only with simple phosphanes but also with phosphites such as P(OMe) 3 . [7] These Fe II complexes all have planar porphyrin core conformations.…”