Carbonylation of iron(II) halide in the presence of chelate diphosphine ligands. Molecular structure of a novel intermolecular adduct [FeC12(dppe)2][Fe2(CO)2Cl4]

Abstract Treatment of tetrahydrofuran solution of FeC1 2 · 4H 2 0 or FeX 2 (X = Br, I) and chelate diphosphines L 2 [L 2 = i BuN(PPh 2 ) 2 , i BuN(PPh 2 ) 2 , i Ph 2 PCH,CH,PPh 2 (dppe)] with carbon monoxide at room temperature and atmospheric pressure gives trans -Fe(CO) 2 X 2 L 2 (X = Cl, Br, 1) in high yields. Their IR, 31 PNMR spectra and X-ray crystallography prove that they have the structures of trans -carbonyls and cis -halogens. Reaction of FeC1 2 · 4H 2 0 and dppe with carbon monoxide gives a novel cage intermolecular adduct in which the active species of Fe 2 (CO) 2 Cl 4 is stabilized by the cage structure of FeCl 2 (dppe) 2 in crystalline state. The structures of Fe(CO) 2 I 2 [ i BuN(PPh 2 ) 2 ] ( 1 ) and [FeCl 2 (dppe) 2 ][Fe2(CO) 2 Cl 4 ] ( 8 ) are determined by X-ray crystallography. Compound 1 crystallizes in the space group P 1 , with a = 9.605(2), b = 10.295(2), c = 17.219(4) A, α = 97.86, β = 94.98(2), γ = 109.16(2)°, and Z = 2, R = 0.071, Rw = 0.080. Compound 8 crystallizes in the space group P 1 , with a = 9.874(2), b = 10.576(1), c = 13.347(4) A, α = 86.09(2), β = 85.05(2), γ = 81.43(1)°, and Z = 1, R = 0.078, Rw = 0.082.