Fe CO 4L complexes

Ligand Method of production Crystal structure known Yield (%) References 

Mononuclear Iron Carbonyls without Hydrocarbon Ligands 

Time-dependent DFT was used to study the photochemistry of Fe(CO)4PH3. The aim of the study was to determine whether the complex would expel PFIs or Results indicated that the excited FefCOlaPFIs complex 

Various mononuclear iron carbonyl complexes with a single water-soluble phosphine ligand were synthesized of the form Fe(CO)4L, L = [Ph2P(CFl2) PMe3] ( = 2, 3, 6, 10). Small amounts of the disubstituted complexes were also formed, as shown in Equation (56).  

Tris(amido)phosphines 40-43 react with Fc2(CO)9 to give mononuclear iron carbonyl complexes Fe(CO)4(PR3). IR data collected from these complexes, combined with data from similar complexes, revealed the TT-acidity of the phosphines to be 41 w 40 43 P(OPh 3 42 PPh3 P(NMe2)3- Variable-temperature NMR on the Fe(GO)4 complexes of 41-43 showed rapid exchange of axial and equatorial carbonyls from —80 to 20 °C, while complex 40 showed slow axial-equatorial carbonyl exchange even at room temperature, attributed to the steric bulk and rigidity of the ligand. 

---

A better synthesis (89% yield) of Fe(CO)3(PPh3)2 is reported from [PPN]2[Fe4(CO)i3], where PPN+ = bis(triphenylphosphine)iminium. The C0X2 (X = Cl, Br, I) catalyzed substitution of CO in Fe(CO)j is reported to yield Fe(CO)4L species in 15 to 99% yield and Fe(CO)3(PPh3)2 was prepared (net 62% yield) from Fe(CO)s in a two-step procedure that requires a chromatographic separation. Strohmeier and Muller report that irradiation of Fe(CO)s in the presence of several phosphines produces Fe(CO)3L2 and Fe(CO)4L complexes in yields that range from 13% for the synthesis of Fe(CO)3[P(/i-Bu)3]2 to 35% for Fe(CO)3[P(c-C6Hn)3]2. For some of the compounds synthesized, vacuum sublimation is necessary to separate the Fe(CO)3L2 species from Fe(CO)4L. The one-step photochemical procedure we report here employs cyclohexane as a solvent. That enables unreacted phosphine, Fe(CO)s, and Fe(CO)4L to remain in solution while pure Fe(CO)3L2 precipitates. It is essential that the phosphines used in these reactions be free of phosphine oxides, which labilize CO and yield products other than Fe(CO)3(PR3)2 complexes. 

TABLE I. Reaction Conditions and Spectroscopic Data for the Complexes Fe(CO)4L [L = PPh3, AsPh3, SbPh3, PMePh2,... 

This has already been discussed in relation to n bonding in Fe(CO)4P OC(CF3)2CN 3 and is confirmed by the fact that the majority of M(CO)4L complexes are axially substituted, since the... 

Wilkinson (9) isolated the tetrakis(trihalogenophosphine)nickel compounds Ni(PX3)4 (X= F, Cl, Br), and Behrens (10) isolated the triphenylphosphine complex Ni[P(C6H5)3]4 via [Ni(CN)4]4. With iron pentacarbonyl, isonitriles and phosphines yield (11) mono- and disubstituted derivatives, Fe(CO)4L and Fe(CO)3L2, respectively, the latter being the well-known cyclization catalyst of Reppe (7). With the same ligands, carbonyls of the chromium group afforded pentacarbonyl derivatives M(CO)5L. However,... 

The data in Table III for the photochemical isomerization of 1-pentene show that photochemical activation is also a viable means of sample activation. During these reactions, CO gas is given off and it is believed from solution studies that an Fe(C0)4L complex is initially formed. The Fe(C0) L complex, where L is a bound pentene, can then undergo isomerization to the cis and trans isomers of 2-pentene. The data in Table III show that the incorporation of a zeolite not only changes the product distribution from a 2.0 ratio of the trans to the cis, as observed in solution studies, but that the photolysis time is relatively short. It should be recognized here that high energy ultraviolet radiation is used, but the photon flux is relatively low. The kinetics of this reaction are surely different from that of the solution reactions and it is not inconceivable that there are steric constraints administered by the zeolite... 

---