Iron complexes solvent effect

In this paper we shall extend our earlier interpretation of the redox results to the nmr data for the N - CH2 protons in tris(N,N-diethyldithiocarbamato) iron(III). We shall show that the solvent dependence of the nmr shifts can be interpreted as arising from solvent interactions with the iron(III) dithiocarbamate system. Although the solvent interactions are small compared with the electronic interactions within the transition metal iron complex the effect is marked since in these cases for the d iron system there are low lying electronic states where the energy separation is sensitive to small changes in the crystal field environment of the transition metal ion. 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

An iron complex-catalyzed asymmetric hydrosilylation of ketones was achieved by using chiral phosphoms ligands [68]. Among various ligands, the best enantios-electivities (up to 99% ee) were obtained using a combination of Fe(OAc)2/(5,5)-Me-Duphos in THF. This hydrosilylation works smoothly in other solvents (diethylether, n-hexane, dichloromethane, and toluene), but other iron sources are not effective. Surprisingly, this Fe catalyst (45% ee) was more efficient in the asymmetric hydrosilylation of cyclohexylmethylketone, a substrate that proved to be problematic in hydrosilylations using Ru [69] or Ti [70] catalysts (43 and 23% ee, respectively). 

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Figure 2 Diagrammatic summary of selected structural, substituent, and solvent effects on rate constants (kj, at 298 K) for base hydrolysis of low spin iron(II)-diimine complexes. Ligand abbreviations not appearing in the list at the end of this chapter are apmi = (73) with = Me BOH cage = (78) with X = OH ...

P. Vogel s group studied exhaustively the 5,6,7,8-tetramethylidenebicyclo[2.2.2]octane system and its metal carbonyl complexes. The preparation and CD spectra of tricarbonyl-iron complexes (144-147) were reported333. The chirality of complexes 144 and 146 is due uniquely to the coordination of Fe(CO)3 moieties. The signs of the Cotton effects for (+)-144 and (+)-146 obey the octant rule, as the endo-Ft(CO)j, of 144 and 146 fall in a positive octant, while the second exo-Fe(CO)3 (syn to the carbonyl) lies almost on the XY nodal plane, and thus its contribution is expected to be small. The deuterium-substituted free tetraenone 148, however, showed an anti-octant behavior. The CD spectra of 144 and 146 are strongly temperature and solvent dependent. 

A remarkable solvent effect on the chemoselectivity was discovered by Agarwala and Bandyopadhyay (Scheme 3.24, B) [114]. When cyclohexene la was oxidized with tBuOOH in the presence of an electronegative substituted iron(III) porphyrin complex in CH2Cl2-MeOH, epoxide 4a was the predominant product (69% yield) in addition to alcohol 2a and ketone 3a as byproducts in 20% and 11% yields,... 

The magnetic moments rise only slightly at elevated temperatures (see Table 5), which led the authors to conclude that some population of the higher sT2(Oh) state is possible. No clear distinction can be made as to which of the influencing factors, viz. electronic effects, steric hindrance, and crystal solvent effects, plays the dominant role here, because all of these are operative to some extent. Data from the UV-vis spectra of the nickel(II) complexes indicate that the ligands have field strengths in the iron(II) crossover region. 

The solvent effects on PT reactions begin to become important when reactants and products are solvated differently as in the example below involving iron complexes. 

There has been a report of a study of the photodissociation of carbonmonoxy-iron(II) porphyrin complexes. The reactions were monitored by Mossbauer spectroscopy, which showed a transition from the low-spin to the high-spin state accompanying loss of CO, and a pronounced solvent effect on recombination rates. 

We considered the possibility of the positive effect of small amounts of water on the rate of the transformation of iron complexes with R4NBr and probably on the parameters SPEH and C in the ethylbenzene oxidation, catalyzed (Fe(III)(acac)3 + I NBr. Outer sphere coordination of H20 molecules may promote the stabilization of intermediate zwitterions L2(L ML1 02 ) and as a consequence the increase in the probability of the regioselective addition of 02 to nucleophilic y-C atom of (acac)- ligand can be expected [14], It is well-known that the stability of zwitterions increases in the presence of the polar solvents [14], The H - bond formation between H20 molecule and zwitterion may also promote the proton transfer inside of the zwitterion followed by the zwitterion conversion into the products via Scheme 1 [15], It is known the cases of the increase in the ratio of alkylation s products on y-C atom of the R4N(acac) in the presence of insignificant additives of water ( 10 3 MOJib/n) as compared to the alkylation s reaction in the non proton solvents [16],... 

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