MOLECULAR-STRUCTURE AND REACTIONS OF AZOBENZENE COMPLEXES WITH IRON-LITHIUM COMPOUNDS

Reactions of azobenzene have been studied with heteronuclear iron-lith ium compounds formed in the reaction of FeCl3 with LiPh, one of the di nitrogen reducing systems of the Vol'pin type: Ph4FeLi4( OEt2)(4) (1) and (H-2)FePh4Li4 (OEt2)(4) (2). The structures of the azobenzene comp lexes formed, (N2Ph2)(3)FeLi3(OEt2)(3) (3) and (N2Ph2)(3)FeLi2(THF)(2) (4), as well as an ether-containing analog of the latter. ( N2Ph2)(3) FeLi2( OEt2)(2) ( 5), were determined by X-ray analysis of single crys tals. Coordination of azobenzene at FeLi3 and FeLi2 clusters was shown to result in a significant elongation of the NN bond; partial cleavag e of this bond on protolysis of the complexes resulted in the formatio n of hydrazobenzene and aniline. Magnetic susceptibility measurements and theoretic analysis of a similar model complex leads to the conclus ion that the iron oxidation state in 3 may be considered between iron( I) and iron(III) (close to iron(I)), whereas in 4 and 5 it is close to iron(II). (C) 1998 Elsevier Science S.A. AU rights reserved.