A Phosphorus Analogue of Bis(η⁴‐cyclobutadiene)iron(0)

Abstract

P makes it possible: The convenient oxidative synthesis of the 16-electron organophosphorus iron sandwich complex [Fe(eta(4)-P(2)C(2)tBu(2))(2)] (see structure) suggests that the elusive all-carbon complex [Fe(eta(4)-C(4)H(4))(2)] is a viable synthetic target.

Heteroatom‐Free Arene‐Cobalt and Arene‐Iron Catalysts for Hydrogenations

“…[10][11][12] Unambiguous distinction between homogeneous and heterogeneous catalysts is intricate, [21] yet our observations are consistent with a homogeneous mechanism. The loss of suitable p acceptors after complete hydrogenation of 1-dodecene (and 2 % anthracene from the precatalyst) resulted in catalyst precipitation.…”

“…[6b,c] A PNP pincer ligand was recently used by Hanson and coworkers to stabilize a cobalt catalyst with 15 valence electrons that allowed hydrogenation of alkenes, ketones, and imines after activation by Brookharts acid. [10,11] Unlike many catalytic reactions where this scenario would entail catalyst aggregation and deactivation, the presence of a large excess of p-acidic ligands in hydrogenations (of unsaturated molecules such as alkenes, arenes, and carbonyl compounds) can effect rapid ligand exchange between p ligands and thus assure prolonged catalyst activity in the homogeneous phase. [8] The same research group reported high activities of bis(imino)pyridine-and bis(arylimidazol-2-ylidene)pyridine-iron and -cobalt catalysts bearing two labile N 2 ligands (Scheme 1).…”

Iron–iron bonding versus iron–phosphorus bonding in binuclear diphosphacyclobutadiene iron carbonyl complexes

“…The recent discovery by Lammertsma and co-workers in 2008 of metal sandwich complexes of the diphosphacyclobutadiene ligands [4,6,7] makes of interest the structures and thermochemistry of related metal carbonyl derivatives. In this connection, the lowest energy (Me 2 C 2 P 2 ) 2 Fe 2 (CO) 5 structure is found to have one bridging g 1 ,g 4 -Me 2 C 2 P 2 ring as well as a terminal g 4 -Me 2 C 2 P 2 ring and an iron-iron distance of $4.3 Å far too long for a direct ironiron bond.…”

“…[5] This nickel sandwich has the favored 18-electron configuration and is particularly stable. More recently (2008) Lammertsma and coworkers have used the displacement of coordinated anthracene from the cobalt and iron [(g 4 -C 14 H 10 ) 2 M] À anions (M = Co, [6] Fe [7]) with four equivalents of Bu t C"P:to synthesize the anionic sandwich compounds [(g 4 -Bu t 2 C 2 P 2 ) 2 M] À . The corresponding neutral sandwich compounds (g 4 -Bu t 2 C 2 P 2 ) 2 M (M = Co, Fe) were then obtained by oxidation of these anions with (g 5 -C 5 H 5 ) 2 Fe + .…”

Di‐tert‐butyldiphosphatetrahedran: Katalytische Synthese des freien Phosphaalkin‐Dimers

“…Aufbauend auf unsere bisherigen Arbeiten zur Eisen(‐I)‐ und Cobalt(‐I)‐vermittelten Phosphaalkindimerisierung, begannen wir vor kurzem, analoge Reaktionen von Phosphaalkinen mit Nickel(0)‐Verbindungen zu untersuchen. Bei der Reaktion von [Ni(CO) 4 ] mit einem Überschuss an t Bu‐C≡P (50 Äquivalente) zeigte das 31 P{ 1 H}‐NMR‐Spektrum der Reaktionslösung unerwartet ein hochfeldverschobenes Singulett bei −468.2 ppm neben dem Signal des freien t Bu‐C≡P bei −68.1 ppm.…”