The interactions between pendant amines in the second coordination sphere and ligands in the first coordination sphere are important for understanding the structures and reactivity of complexes containing P R 2 N R′ 2 ligands, which have been shown to be highly active H 2 oxidation/production catalysts. A series of [Fe(P Ph 2 N Bn 2 ) 2 (X)(Y)] n+ complexes have been prepared and structurally characterized. These complexes have two different ligands with which the pendant amines of the diphosphine ligand can interact. The solid state structure of cis-Fe(P Ph 2 N Bn 2 ) 2 Cl 2 reveals that the six-membered rings adjacent to the P atoms are in a boat confirmation, resulting in close N⋯P distances that suggests the P atoms have a greater affinity for the lone pair of electrons on the N atom than chloride ligands. Similarly, boat conformations are observed for both rings adjacent to the hydride ligands of trans-[HFe(P Ph 2 N Bn 2 ) 2 (CH 3 CN)] + and trans-HFe(P Ph 2 N Bn 2 ) 2 Cl, resulting in short N⋯H distances. Spectroscopic and computational studies of trans-[HFe(P Ph 2 N Bn 2 ) 2 (CO)] + , trans-[HFe(P Ph 2 N Bn 2 )(P Ph 2 N Bn 2 H)(CO)] 2+ , and trans-[HFe(P Ph 2 N Bn 2 ) 2 (H 2 )] + indicate the complexes are more stable when the pendant amines in boat conformations are adjacent to the hydride ligand. These data suggest an attractor ordering of H - > CO > H 2 > PR 3 > Cl - ∼ CH 3 CN.
ASJC Scopus subject areas
- Inorganic Chemistry