HIGHLY DISTORTED DIIRON(II,II) COMPLEXES CONTAINING 4 AMIDINATE LIGANDS - A LONG AND A SHORT METAL-METAL DISTANCE .2.

The reaction of FeCl2(HDPhF)(2) (HDPhF=N,N'-diphenylformamidine) with methyllithium in Et2O followed by extraction into solvent mixtures con taining THF, toluene and hexanes produces crystals of Fe-2(mu-DPhF)(4) (I). This dinuclear compound contains four formamidinato bridges but i n an arrangement that is highly distorted compared to the known paddle -wheel structures of M-2(amidinato)(4) molecules. A similar reaction u sing FeCl2(HDPhBz)(2) (HDPhBz=N,N'-diphenylbenzamidine) also gives a d istorted molecule Fe-2(mu-DPhBz)(2)(eta(2)-DPhBz)(2) . 2THF (II), in w hich two amidine groups form bridges between the metal centers while t he other two groups chelate to an iron atom each. The Fe-Fe distances are 2.462(2) and 3.124(1) Angstrom, respectively. Both compounds I and II have been structurally characterized by X-ray crystallography. At -60 degrees C, crystal data for I are: monoclinic, space group I2/a, a =18.001(6), b=10.019(1), c=25.422(9) Angstrom, beta=105.28(1)degrees, Z=4. For II: triclinic, space group <P(1)over bar>, a=10.7874(6), b=13 .1756(7), c=13.4552(8) Angstrom, alpha=99.89(1), beta=109.405(3),gamma =100.210(7)degrees, Z=1.