SYNTHESIS AND CHARACTERIZATION OF [(2,4,6-(CH3O)3C6H2)3P=O]FECL3 - A 4-COORDINATE PHOSPHINE OXIDE ADDUCT OF FECL3

The 1 : 1 reaction between anhydrous ferric chloride and tris(2,4,6-tri-methoxyphenyl)phosphine (TMPP) in benzene produces a reactive complex, 1, with the empirical formula FeCl3(TMPP). This compound undergoes a facile reaction with molecular oxygen at room temperature and 1 atm to give a dark green intermediate and a final orange product, FeCl3[OP{C6H2(OMe)3}3] (3). Crystal data for 3: P1, a = 12.23(1), b = 14.06(1), c = 13.13(1) Å, α = 110.78(7), β = 109.89(8), γ = 72.58(8)°, V = 1648(3) Å3, Z = 2, dcalc = 1.432 g cm-3, μ(Mo-Kα) = 7.976 cm-1, R = 0.068, Rw = 0.078 for 374 parameters and 1606 data with Fo2 > 3σ(Fo)2. The structure consists of a tetrahedrally coordinated iron(III) centre ligated by three chlorides and one phosphine oxide ligand. This is the first example of a four-coordinate phosphine oxide complex of FeCl3 and one of only several known examples of a neutral tetrahedral iron(III) complex. The synthesis and properties of 3 are presented and discussed. © 1990.