PNNL

Abstract

A series of new iron(II) complexes that contain cyclic diphosphine ligands with pendant amine bases, P2RN2R’, have been synthesized and characterized (where P2RN2R’ are substituted 1,5-diaza-3,7-diphosphacyclooctanes). These compounds include [Fe(P2PhN2Ph)(CH3CN)4](BF4)2 (1), cis-[Fe(CH3CN)2(P2PhN2Ph)2](BF4)2 (2a), cis-[Fe(CH3CN)2(P2CyN2Bz)2](BF4)2 (2b), cis-Fe(CH3CN)2(P2PhN2Bz)2](BF4)2 (2c), cis-Fe (P2PhN2Ph)2(Cl)2 (3), and trans-[HFe(CH3CN)(P2PhN2Ph)2](BF4), (4). The molecular structures of 1, 2b, and 4 have been confirmed by X-ray diffraction studies. For all complexes the cyclic diphosphine ligands contain one six-membered ring in a chair conformation and one six-membered ring in a boat conformation. For complex 4, the two rings that are in boat conformations result in N--H distances between the pendant amine nitrogens and the hydride ligand of 2.6 to 2.7 Å. Protonation of the pendant bases in complex 4 have been found to form several products. A structural assignment for a dominant protonated isomer has been assigned on the basis of 1H, 31P and 15N spectroscopic techniques. This work was supported by Grant CHE-0240106 from the National Science Foundation. D. L. D. acknowledges the support of the Office of Basic Energy Sciences of the Department of Energy, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.