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Lagaditis PO, Mikhailine AA, Lough AJ, Morris RH: Template synthesis of iron (II) complexes containing tridentate P-N-S, P-N-P, P-N-N, and tetradentate P-N-N-P ligands. Inorg Chem. 2010 Feb 1;49(3):1094-102.
A series of mer-tridentate iron (II) complexes bearing P-N-S (3), P-N-P (4), and P-N-N (5) ligands have been prepared via the metal template effect in one pot involving air-stable phosphonium dimers [cyclo-(-PPh (2) CH (2) C (OH) H-)(2)](Br)(2) (1) and [cyclo-(-PCy (2) CH (2) C (OH) H-)(2)](Br)(2) (2), KOtBu, [Fe (H (2) O)(6)][BF (4)](2) and 2-aminothiolphenol (for 3), 2-(diphenylphosphino) ethylamine (for 4), and 2-(aminomethyl) pyridine (for 5). The new phosphonium dimer 2 was prepared via an S (N) 2 reaction of PCy (2) H with BrCH (2) CH (OEt)(2). The complexes Fe{PR (2) CH (2) CH=N (2-C (6) H (4)) S}(2) FeBr (2) (3a, R = Ph; 3b, R = Cy) are paramagnetic, and X-ray diffraction studies revealed that they are bimetallic, in which the S atoms of the bis-tridentate (PNS)(2) Fe unit bridge to a FeBr (2) fragment. Complexes [Fe (PR (2) CH (2) CH=NC (2) H (4) PPh (2))(NCMe)(3)] X (2) (4a, R = Ph; 4b, R = Cy; X (2) = FeBr (4) or (BF (4))(2)) form when 1 equiv of iron is reacted with PPh (2) CH (2) CH (2) NH (2) and 0.5 equiv of the appropriate phosphonium dimer. The evidence for P-N-P coordination is the large (2) J (PP) coupling constant in the (31) P {(1) H} NMR spectrum for the trans phosphorus nuclei. If 0.5 equiv of [Fe (H (2) O)(6)][BF (4)](2) were added in the synthesis, the complex trans-[Fe (NCMe)(2)(Ph (2) PC (2) H (4) NH (2))(2)][FeBr (4)] (4c) formed, and this has been characterized by X-ray diffraction. Complexes [Fe{PR (2) CH (2) CH=NCH (2)(2-C (5) H (4) N)}(2)](BPh (4))(2) (5) are bis-tridentate iron (II) complexes with pyridyl donors trans to the phosphine donors. Interestingly, addition of the diamines ethylenediamine, (1R,2R)-(-)-1,2-diaminocyclohexane, (1R,2R)-(-)-1,2-diphenylethylenediamine, or o-phenylenediamine, in the template synthesis with 2 led directly to tetradentate P-N-N-P iron (II) complexes trans-[Fe (NCMe)(2)(PCy (2) CH (2) CH=N-Q-N=CHCH (2) PCy (2)](BPh (4))(2) (Q = CH (2) CH (2), 6a; Q = (1R,2R)-cyclo-C (6) H (10), 6b; Q = (1R,2R)-CHPhCHPh, 6c; Q = C (6) H (4), 6d). In contrast, similar reactions under the same conditions with dimer 1 led to complexes mer-[Fe (P-N-N)(2)](2+) as reported previously. Complexes 6a and 6b have been characterized by X-ray diffraction and exhibited large P-Fe-P bond angles of 112.92 (2) and 111.96 (4) degrees, respectively. |
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