Iron‐ and Cobalt‐Catalyzed Synthesis of Carbene Phosphinidenes

Abstract

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3)2}2] (M=Fe, Co), N‐heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)⋅PAr. The formation of (IMe4)⋅PMes (Mes=mesityl) is also catalyzed by the phosphinidene‐bridged complex [(IMe4)2Fe(μ‐PMes)]2, which provides evidence for metal‐catalyzed phosphinidene transfer.

Transition‐Metal Carbonyl Complexes and Electron‐Donating Properties of N‐Heterocyclic‐Carbene–Phosphinidene Adducts

“…The C carbene –P bond lengths range from 1.805(2) Å (in 4c ) to 1.819(3) Å (in 4b ) and are significantly longer than those in the free ligands [1.7510(16) Å for R = H, 1.7658(10) Å for R = Ph, 1.766(2) Å for R = Mes], in agreement with the expected decrease of the C carbene –P bond order upon metal complexation . The metal–phosphorus bond lengths in the pairs 4a / 4b and 5a / 5b are almost identical, whereas the steric demand of the mesityl substituent in 4c affords a slightly elongated W–P bond (Table ).…”

“…In addition, the sterically more encumbered derivative 1c was synthesized analogously to 1b through the potassium graphite reduction of the adduct IPr · PMesCl 2 obtained from the carbene IPr and dichloromesitylphosphine (PMesCl 2 ). However, 1c was isolated in only 8 % yield as a yellow solid, whereas Layfield and co‐workers recently reported the synthesis of 1c from [(IPr)Fe{N(SiMe 3 ) 2 }] and MesPH 2 in 57 % yield . In agreement with the reported spectroscopic data, the 1 H NMR spectrum of 1c in C 6 D 6 shows a septet at δ = 3.28 ppm, and two broad signals at δ = 1.45 and 1.08 ppm for the isopropyl CH and CH 3 hydrogen atoms indicate hindered rotation around the C carbene –P bond.…”

N‐Heterocyclic Carbene–Phosphinidene Adducts: Synthesis, Properties, and Applications

“…Layfield and co‐workers reported that in the presence of stoichiometric or catalytic amounts of [M{N(SiMe 3 ) 2 } 2 ] (M = Fe, Co), N‐heterocyclic carbenes 2 , 5 and 6 react with phenyl or mesitylphosphines at 80 °C to give the carbene–phosphinidene adducts ( 2 , 5 , 6 ) · PPh and ( 2 , 5 , 6 ) · PMes (Scheme ) . The formation of 2· PMes is also catalyzed by the phosphinidene‐bridged complex [( 2 ) 2 Fe(µ‐PMes)] 2 , which provides evidence for metal‐catalyzed phosphinidene transfer.…”

Phosphinidene-bridged binuclear complexes

“…The reaction of the three-coordinate amido complexes [(IMe 4 )M{N(SiMe 3 ) 2 } 2 ] (M= Fe or Co; IMe 4 =1,3,4,5-tetramethylimidazolin-2-ylidene) with PH 2 Mes in the presence of excess carbene yields the dinuclear phosphinidene complexes 74 and 75 after amine elimination (Scheme 40) [76].…”