12290-98-1Relevant academic research and scientific papers
Separation of phosphorus(III) ligands into pure σ-donors and σ-donor/π-acceptors: Comparison of basicity and σ-donicity
Rahman, Md. Matiur,Liu, Hong-Ye,Eriks, Klaas,Prock, Alfred,Giering, Warren P.
, p. 1 - 7 (2008/10/08)
The separation of phosphorus(III) ligands into two distinct groups identified as pure σ-donor ligands and σ-donor/π-acceptor ligands for the acetyl and methyl complexes, (η-Cp)FeL(CO)COMe, (η-Cp′)FeL-(CO)COMe (Cp′ = MeC5H4), and (η-Cp)FeL(CO)Me, is accomplished by correlation of the terminal carbonyl stretching frequencies with the EL°′ values. The basicity (pKa value of HPR3+) is related primarily to the σ-donicity (the ability of a ligand to donate σ-electrons to a transition metal) and to a lesser degree to the size of the ligand. We conclude that pKa values are reasonable measures of the σ-donicity for those ligands that are pure σ-donor ligands; a better measure are the χ values for those ligands that are pure σ-donors for both the iron complex and LNi(CO)3.
Reactions of alkyllithium reagents and nitrogen- and oxygen-based nucleophiles with cyclopentadienyliron-η2-alkyne complexes. Crystal and molecular structure of a diastereomeric mixture of CpFeCO[P(OPh)3][η1-CH(Me)COMe]
Reger, Daniel L.,Klaeren, Stephen A.,Lebioda, Lukasz
, p. 1072 - 1079 (2008/10/08)
Reaction of {[Fe](η2-MeC≡CMe)}+ ([Fe] = CpFeCO[P(OPh)3]) with PhNHLi or NH2R (R = Ph, CH2Ph) followed by base yields the respective [Fe][η1-CH(Me)C(NR)Me] complex. A similar reaction using Ph2NLi yields [Fe](η1-CH2C≡CMe) whereas MeLi yields mainly the ring substitution product (η5-C5H4Me)-FeCO[P(OPh) 3][η1-(E)-C(Me)=C(H)Me]. The complex [Fe][η1-CH(Me)COMe] forms by direct chromatography of the cationic η2-alkyne complex on alumina. X-ray analysis of a crystal composed of a ca. 7:3 mixture of the two diastereomerically related pairs of enantiomers has been carried out. The triclinic crystals are in the space group P1 with a = 12.358 (2) A?, b = 12.576 (4) A?, c = 8.289 (2) A?, α = 96.54 (2)°, β = 95.66 (2)°, γ = 88.08 (2)°, V = 1273 (1) A?3, and Z = 2. MeLi, PhNHLi, and Ph2NLi react with {[Fe](η2-MeC≡CPh)}+ at the cyclopentadienyl ring to yield mainly the respective (η5-C5H4NuC)FeCO[P-(OPh) 3][η1-(E)-C(Me)=C(H)Ph] (Nuc = Me, PhNH, Ph2N) complex. Reaction with t-BuOK yields [Fe](η1-CH2C≡CPh) and with MeOH/Na2CO3 yields [Fe][η1-(E)-C(Me)=C(Ph)OMe], and treatment of the η2-alkyne complex with alumina yields [Fe][η1-CH(Me)COPh]. The complex {[Fe](η2-MeC≡CCO2Me)}+ reacts differently with each of the nucleophiles Et2NLi, Ph2NLi, and PhNHLi to yield respectively [Fe][η1-C(CO2Me)=C=CH2], [Fe][η1-(E)-C(CO2Me)=C(Me)NPh2], and (η5-C5H4NHPh)FeCO[P-(OPh) 3][η1-(E)-C(CO2Me)=C(H)Me]. Reaction with MeOH/Na2CO3 yields [Fe][η1-(E)-C(CO2Me)=C-(Me)OMe] that upon treatment with alumina converts mainly to [Fe][η1-CH(CO2Me)COMe]. Reaction with MeLi is indiscriminate, yielding four products that arise from attack at the ring, attack at the alkyne, deprotonation, and direct addition to the metal. The allene complex {[Fe](η2-CH2=C=CH2)}+ reacts with Et2NLi, Ph2NLi, and MeLi by simple addition to the allene ligand to yield [Fe][η1-C(CH2Nuc)=CH2] (Nuc = Et2N, Ph2N, Me). The complex [Fe]I undergoes ring substitution when treated with Et2NLi to yield (η5-C5H4NEt2)FeCO[P(OPh) 3]I.
