High- and low-spin chelate complexes of iron featuring κ-C,X-CH2C6H4X (X = NMe2, PMe2, PPh2) and κ-C,P-CH2PMe2 ligands

Abstract

Several C,X-chelate complexes of iron were generated via standard metathetical procedures. Treatment of FeCl2 and LnFeCl2 (L = Me2IPr, n = 1; PMe3, n = 2) with anionic equivalents o-LiCH2C6H4NMe2, o-LiCH2C6H4PPh2, and LiCH2PMe2 led to the preparation of [Fe(o-CH2C6H4NMe2)]2(κ-μ-CH2,N-o-CH2C6H4NMe2)2 (1, X-ray), [fac-Fe(κ-C,P-o-CH2C6H4PPh2)3][Li(TMEDA)2] (2, X-ray), (Me2IPr)Fe(CH2C6H4-o-NMe2)2 (3-C,N), [(Me2IPr)2Fe](μ-κ-C,P-CH2PMe2)2[Fe(κ-C,P-CH2PMe2)2] (4, X-ray), and (PMe3)2Fe(κ-C,P-CH2PMe2)2 (5). CH-Bond activation of cis-(Me3P)4FeMe2 with o-CH3C6H4PMe2 led to the generation of trans,cis-(PMe3)2Fe(κ-C,P-CH2C6H4-o-PMe2)2 (6). Exposure of these compounds to [Cp2Fe][PF6], a 1e− oxidant, or AdN3, here construed as a 2e− oxidant, led to degradation in all cases, usually with the generation of carbon-carbon coupled ligands as byproducts. The inability of these systems to permit access to higher iron oxidation states is discussed.