Side-on coordination of diphosphorus to a mononuclear iron center
Shuai Wang, Jeffrey D. Sears, Curtis E. Moore, Arnold L. Rheingold, Michael L. Neidig, Joshua S. Figueroa
Abstract
The diagonal relationship in the periodic table between phosphorus and carbon has set an expectation that the triple-bonded diatomic diphosphorus molecule (P 2 ) should more closely mimic the attributes of acetylene (HC≡CH) rather than its group 15 congener dinitrogen (N 2 ). Although acetylene has well-documented coordination chemistry with mononuclear transition metals, coordination complexes that feature P 2 bound to a single metal center have remained elusive. We report the isolation and x-ray crystallographic characterization of a mononuclear iron complex featuring P 2 coordination in a side-on, η 2 -binding mode. An analogous η 2 -bound bis-timethylsilylacetylene iron complex is reported for comparison. Nuclear magnetic resonance, infrared, and Mössbauer spectroscopic analysis—in conjunction with density functional theory calculations—demonstrate that η 2 -P 2 and η 2 -acetylene ligands exert a similar electronic demand on mononuclear iron centers but exhibit different reactivity profiles.