Highly distorted diiron(II, II) complexes containing four amidinate ligands. A long and short metal-metal distance

Abstract

The reaction of FeCl 2(HDPhF) 2 (HDPhF = N, N′-diphenylformamidine) with methyllithium in Et 2O followed by extraction into solvent mixtures containing THF, toluene and hexanes produces crystals of Fe 2(μ-DPhF) 4 ( I). This dinuclear compound contains four formamidinato bridges but in an arrangement that is highly distorted compared to the known paddle-wheel structures of M 2(amidinato) 4 molecules. A similar reaction using FeCl 2(HDPhBz) 2 (HDPhBz = N, N′-diphenylbenzamidine) also gives a distorted molecule Fe 2( μ-DPhBz) 2( η 2-DPhBz) 2·2THF ( II), in which two amidine groups form bridges between the metal centers while the other two groups chelate to an iron atom each. The FeFe distances are 2.462(2) and 3.124(1) Å, respectively. Both compounds I and II have been structurally characterized by X-ray crystallography. At −60°C, crystal data for I are: monoclinic, space group I2/a, a = 18.001(6), b = 10.019(1), c = 25.422(9) A ̊ , β = 105.28(1)°, Z = 4 . For II: triclinic, space group P 1 ̄ , a = 10.7874(6), b = 13.1756(7), c = 13.4552(8) A ̊ , α = 99.89(1), β = 109.405(3), γ = 100.210(7)°, Z = 1 .