Side-on coordination of diphosphorus to a mononuclear iron center

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.

Synthesis and Reactivity of a Cyclooctatetraene‐Like Polyphosphorus Ligand Complex [Cyclo‐P8]

“…Besides organic substitution, oligo‐phosphorus species can also be stabilized via coordination to transition metals. Very prominently, the Figueroa group recently was able to stabilize the elusive P 2 at a mononuclear iron center [7] . Besides, several completely unsubstituted cyclic P n ligands ( n =3–6), could be stabilized within the coordination sphere of transition metals (Scheme 1a).…”

“…Very prominently, the Figueroa group recently was able to stabilize the elusive P 2 at a mononuclear iron center. [7] Besides, several completely unsubstituted cyclic P n ligands (n = 3-6), could be stabilized within the coordination sphere of transition metals (Scheme 1a). While cyclo-P n (n = 3-5) ligands can be obtained within sandwich type complexes (II, [8] III, [9] IV [10] ), cyclo-P 6 (V) [11] could this far only be obtained within triple-decker complexes.…”

Synthese und Reaktivität eines Cyclooctatetraen‐artigen Polyphosphor‐Ligandkomplexes [Cyclo‐P8]

“…Neben der organischen Substitution können Oligophosphor‐Spezies auch über die Koordination an Übergangsmetalle stabilisiert werden. Ein herausragendes Beispiel dafür ist die unlängst gelungene Stabilisierung des schwer fassbaren P 2 Moleküls an einem einkernigen Eisenkomplex durch die Figueroa Gruppe [7] . Daneben konnten mehrere vollständig unsubstituierte cyclo ‐P n ‐Liganden ( n =3–6) innerhalb der Koordinationssphäre von Übergangsmetallen stabilisiert werden (Schema 1a).…”

“…Ein herausragendes Beispiel dafür ist die unlängst gelungene Stabilisierung des schwer fassba-ren P 2 Moleküls an einem einkernigen Eisenkomplex durch die Figueroa Gruppe. [7] Daneben konnten mehrere vollständig unsubstituierte cyclo-P n -Liganden (n = 3-6) innerhalb der Koordinationssphäre von Übergangsmetallen stabilisiert werden (Schema 1a). Während cyclo-P n -Liganden (n = 3-5) in Sandwichkomplexen (II, [8] III, [9] IV [10] ) erhalten werden konnten, erfolgte die Bildung von cyclo-P 6 (V) [11] bisher lediglich bei Triple-Decker-Komplexen.…”

Synthesis and Reactivity of Hetero‐Pnictogen Diazonium Analogs Stabilized by Transition Metal Units

“…[12] In addition, the group of Figueroa succeeded in isolating the mononuclear iron complex [(CNAr Dipp2 ) 2 (CO) 2 Fe(η 2 -P 2 )] (Ar Dipp2 = 2,6-(2,6-C 6 H 3 i Pr 2 )C 6 H 3 ) featuring a first side-on coordinated P 2 ligand at one metal, which can be considered as the heavier dinitrogen homolog (Scheme 1c). [13] Earlier on, several complexes bearing P 2 units were synthesized, which, however, require additional stabilization by at least two transition metals. [14] Diazonium salts [N�NÀ R][X] (R = aryl, alkyl) were first reported as early as 1858 [15] and have been important starting materials in organic syntheses ever since.…”