Structure and reactivity of iron(II) complexes of a polymerizable bis-phosphine ligand

Iron(II) complexes of 1,2-bis(diallylphosphino)ethane (TAPE) were explored as a possible route to polymeric materials that would reversibly bind N-2 and H-2. A new synthetic route to the TAPE ligand was developed. Starting with the trans-Fe(TAPE)(2)Cl-2 complex, a series of iron(II) complexes was synthesized having the general formula FeL2(A)(B) where L = TAPE and (A)(B) = (Cl)(CH3CN); (CH3CN)(CH3CN); (H)(CH3CN) and (H)(Cl). These substitution reactions of the trans-Fe(TAPE)(2)Cl-2 complex were easily monitored using both P-31 NMR and UV-Vis spectroscopy, and the product complexes were crystallographically characterized as having trans stereochemistry. Structural metrics of the complexes are most similar to complexes with 1,2-bis(diethylphosphino)ethane (DEPE). At atmospheric pressure, dinitrogen does not bind to the iron when the trans ligand is chloride. Isolation of the nitrogen adduct when the trans ligand is hydride was complicated by a novel intramolecular hydrogenation of the pendant allyl groups of the phosphine ligand. (C) 2012 Elsevier Ltd. All rights reserved.