A Ligand‐Driven Geometry Switch in Octahedral and Trigonal‐Bipyramidal Iron Complexes Containing (H)PNO and PNN Ligands

Abstract

Complexation reactions of FeII and FeIII salts with the tridentate ligands 2‐(diphenylphosphanyl)benzaldehyde benzoylhydrazone [(H)PNO] and N‐[2‐(diphenylphosphanyl)benzylidene]‐2‐(2‐pyridyl)ethanamine (PNN) was carried out. For (H)PNO, reaction of a stoichiometric amount of anhydrous FeCl2 in the presence of a primary alcohol such as MeOH, EtOH or nBuOH gave the mixed‐valence FeII/FeIII paramagnetic complex [Fe{κ3‐(H)PNO}2]Cl[FeCl4], whereas the reaction between FeCl2 and a twofold excess of (H)PNO in the presence of AgOTf (OTf = triflate, OSO2CF3) led to the isolation of the bis‐chelate paramagnetic ferrous complex [Fe{κ3‐(H)PNO}2][OTf]2. A diamagnetic bis‐chelate ferrous complex [Fe{κ3‐(PNO)2}] was instead obtained from the reaction of FeCl2 with a twofold excess of (H)PNO in the presence of NaOMe. In the case of the PNN ligand, the 1:1 reaction with FeCl2 gave the neutral paramagnetic trigonal‐bipyramidal complex [Fe(κ3‐PNN)Cl2]. The X‐ray structures of [Fe{κ3‐(H)PNO}2]Cl[FeCl4], [Fe2{κ3‐(H)PNO}2Cl6] and [Fe(κ3‐PNN)Cl2] are reported, together with CV and magnetic susceptibility measurements and an ab initio study aimed at rationalizing the different stoichiometries and structures observed with the two tridentate ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Template Synthesis of Iron(II) Complexes Containing Tridentate P−N−S, P−N−P, P−N−N, and Tetradentate P−N−N−P Ligands

“…Crystals of 5a were grown by the slow diffusion of Et 2 O into a MeOH/MeCN (1:1 by volume) solution but were not of good quality for an X-ray diffraction study because they tended to twin. Nonetheless, the X-ray diffraction data supported a mer -octahedral arrangement of the P−N−N ligands about iron, as expected and observed in similar complexes with P−N−N ligands either involving a terminal pyridine or amine (−NH 2 ) donor. , Unlike complexes 4 , complexes 5 are very stable in solution under an inert atmosphere and have considerable stability in the solid state in the air, with minimal decomposition after a week.…”

Cobalt Phosphino-α-Iminopyridine-Catalyzed Hydrofunctionalization of Alkenes: Catalyst Development and Mechanistic Analysis

“…The imine CN distances are elongated by ca. 0.1 Å in comparison to those observed for the PNpy ligands on metal dihalide complexes in Table . , This elongation is consistent with an η 2 -imine ligand where significant electron density is transferred from the metal center. , The Co–Co distances of ca. 2.9 Å are well above the range for bonding .…”

Imine-Centered Reactions in Imino-Phosphine Complexes of Iron Carbonyls

“…Although π-bonded aldehyde complexes have been characterized, 22 η 2 -imines are more typical for early metals: 23 e.g., metallaaziridines. 24 Iron phosphine-imine complexes typically are N-bonded, 11,12,17,25 although a ferraaziridine has been recently reported. 12 Examples of Fe(0) containing π-bound aldimines have been reported: 26 e.g., [Fe(DIP)] 2 (DIP = NC 5 H 3 -2,6-(CHNAr) 2 , Ar = 2,6-C 6 H 3 ( i Pr) 2 ).…”

“…Other phosphine-imine complexes of iron have been described. 17,18 In contrast to the extensive work on tri-and tetradentate phosphine-imines, relatively little effort has focused on the properties of iron complexes of simple bidentate phosphineimines. To probe this area, the present report examines the iron derivatives of Fe(0), Fe(I), and Fe(II) oxidation states.…”