Bis iron complexes

Fig. 7 Systemic spherical name for bis iron complex of Figures 2-21 and 2-22...

Iron and Ruthenium.—Reaction of 3-bromotetrafluorophenyl-lithium with (77-C5H6)2Fe(CO)2l yields complex (217 X = Br), which reacts with n-butyl-lithium at -78 °C to yield a lithio-derivative (217 X = Li), hydrolysed by water to complex (217 X = H), which reforms the lithium compound with n-butyl-lithium this yields the bis(iron) complex (218) with further (7r-C5H5)Fe(CO)2l. Pentafluorobenzenesulphonyl chloride reacts with... 

Mixed arene-2,5-dihydro-l,2,5-thiadiborole-iron complexes have been synthesized by a novel route thermally unstable bis(arene)iron sandwich complexes, prepared by cocondensation of iron atoms with arene, react in the temperature range of -100 to -60°C with free Et2C2B2Mc2S to form reactive intermediates that decom-... 

Bis(imino)pyridine iron complex 5 as a highly efficient catalyst for a hydrogenation reaction was synthesized by Chirik and coworkers in 2004 [27]. Complex 5 looks like a Fe(0) complex, but detailed investigations into the electronic structure of 5 by metrical data, Mossbauer parameters, infrared and NMR spectroscopy, and DFT calculations established the Fe(ll) complex described as 5 in Fig. 2 to be the higher populated species [28]. 

Scheme 7 Intramolecular arene coordination in bis(imino)pyridine iron complex 10...

Bis(imino)pyridine iron complex 5 acts as a catalyst not only for hydrogenation (see 2.1) but also for hydrosilylation of multiple bonds [27]. The results are summarized in Table 10. The reaction rate for hydrosilylations is slower than that for the corresponding hydrogenation however, the trend of reaction rates is similar in each reaction. In case of tra s-2-hexene, the terminal addition product hexyl (phenyl)silane was obtained predominantly. This result clearly shows that an isomerization reaction takes place and the subsequent hydrosilylation reaction dehvers the corresponding product. Reaction of 1-hexene with H2SiPh2 also produced the hydrosilylated product in this system (eq. 1 in Scheme 18). However, the reaction rate for H2SiPh2 was slower than that for H3SiPh. In addition, reaction of diphenylacetylene as an atkyne with phenylsilane afforded the monoaddition product due to steric repulsion (eq. 2 in Scheme 18). 

Scheme 23 Flydrosilylation catalyzed by a bis(imimo)pyridine iron complex...

The comparison of a bis(imino)pyridine iron complex and a pyridine bis (oxazoline) iron complex in hydrosilylation reactions is shown in Scheme 24 [73]. Both iron complexes showed efficient activity at 23°C and low to modest enantioselectivites. However, the steric hindered acetophenone derivatives such as 2, 4, 6 -trimethylacetophenone and 4 -ferf-butyl-2, 6 -dimethylacetophenone reacted sluggishly. The yields and enantioselectivities increased slightly when a combination of iron catalyst and B(CeF5)3 as an additive was used. 

Scheme 24 The comparison of a bis(imino)pyridine iron complex and a pyridine bis(oxazoline) iron complex for hydrosilylation of ketones...

In 2009, Chirik reported a hydrogen-mediated reductive enyne cyclization catalyzed by the bis(imino)pyridine iron complex 5 (Scheme 37) [119]. In the... 

As an alternative method for the C-C bond formation, oligomerization and polymerization reactions of olefins catalyzed by a bis(imino)pyridine iron complex are also well known (Scheme 40) [121-124]. 

A head-to-head dimerization of a-olefin catalyzed by a bis(imino)pyridine iron complex has been reported by Small and Marcucci [126]. This reaction delivers linear internal olefins (up to 80% linearity) from a-oleftns. The linearity of products, however, depends on the catalyst structure and the reaction conditions. 

Fink and Babik reported that propylene polymerization was achieved by a bis (imino)pyridine iron complex with Ph3C[B(C6p5)]4] and ttialkylaluminium as additives [127]. Both 3-methyl-"butyl and "butyl endgroups were observed by NMR spectrum when ttiisobutylaluminium as an activator was used, whereas the only "propyl endgroup was formed in case of triethylaluminium activation. In addition, this polymerization proceeds two times faster with than without a hydrogen atmosphere, but the value decreases and the M IM value rises up. 

The immobilization of metal catalysts onto sohd supports has become an important research area, as catalyst recovery, recycling as well as product separation is easier under heterogeneous conditions. In this respect, the iron complex of the Schiff base HPPn 15 (HPPn = iVA -bis(o-hydroxyacetophenone) propylene diamine) was supported onto cross-linked chloromethylated polystyrene beads. Interestingly, the supported catalyst showed higher catalytic activity than the free metal complex (Scheme 8) [50, 51]. In terms of chemical stability, particularly with... 

Power and coworkers prepared the iron(V) bis-imide complex 3,5-Pr2 Ar Fe[N (1-Ad)]2l [42]. This complex has been characterized by X-ray crystallography with the iron in planar three-coordinate geometry. The Fe-N bond distances are 1.642(2) and 1.619(2)A. Magnetic studies of 3,5-Pr2 Ar Fe[N(l-Ad)]2 reveals that this complex has a low-spin cP configuration with S = jl ground state. This compound is notable as it is a stable Fe(V) imide being well characterized. 

Konig and others published in the 1970s an impressive series of studies on six-coordinate iron(II)-bis-phenanthroline complexes [160-164] for which they inferred 5=1 from thorough magnetic susceptibility and applied-field Mossbauer measurements. Criteria for the stabilization of the triplet ground state for six-coordinate compounds with tetragonal ( >4 ) and trigonal ( >3 ) symmetry were obtained from LFT analyses [163], The molecular structures, however, were not known because the materials could not be crystallized. 

The known reactions involving transfer of a C5HSBR ligand are collected in Table VII. Alternative syntheses are available for the bis(borata-benzene)iron complexes 65 and 18 only (55). In the system 7/Ni(CO)4 the main product is Co(CO)2(C5H5BMe) (15), and 66 is obtained as a thermally unstable by-product (47). In solution, 66 adopts a folded, doubly CO-bridged structure with a dihedral angle of 121° for the Ni2(CO)2 moiety (47). 

The first report of catalyzed chain growth on aluminum was presented by Samsel et al., using metallocenes of actinides [13] or hafnium [14, 15], Gibson et al. described a detailed study of chain growth using the bis(imino)pyridyl iron complex 1 in combination with several metal alkyls [16], Other systems reported to... 

Within group 8, a bis-dinitrogen complex of an iron(O) tridentate pyridinediimine structure has also recently been shown to catalyze the hydrosilylation of alkyne.60 This discovery is a new example of the utility of low-valent iron in catalysis.61... 

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