Solvent effects with iron complexes

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... 

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 ...

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,... 

A particular method for studying complexes of iron is Mossbauer spectroscopy [7]. For instance, a- and p modifications of Fe(Pc) were studied by this method [8], and the dioxygen derivatives, as well. It was found that the oxygen molecule interacts with the complex, and (p-Oxo)-bis-phthalocyaninato-iron(lll) is formed [9]. The stability of the complex depends strongly on the solvents, e.g. in presence of strong N-bases the Fe ll) form is restored at room temperature, even in presence of oxygen [10]. Further, the Y-zeolite encaged Fe(Pc) was also studied, namely stabilization of the pyridine complex, Fe(Pc)(Py)2, as well as the effects of preparation conditions and presence of various counterions in the framework (Na, K, Rb) on the formation of Fe(Pc)(Py)2 are reported [11-13]. 

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],... 

The situation is considerably different for the iron(III) analog (TPPS)Fe "(H20)2 which is hexacoordinate in aqueous solution. In this case the reaction with NO is considerably slower (kon = 4.5 x 10 s ) and kojr (500 s ) is sufficiently large to be measurable by the flash photolysis method as well [92]. Temperature and hydrostatic pressure effects were probed and AH, AS and AV values of 69 + 3 kj mol , 95 10 J mol K and +9+1 cm mol were determined for the "orf reaction and 76 + 6 kJ mol , 60 + 11 ) mol and 18 + 2 cm mol respectively, for the off reaction [93j. The activation parameters for the on reaction compare very favorably with those measured for exchange between coordinated and solvent water for aqueous solutions of (TPPS)Fe "(H20)2 [94] and indicate that kinetics for the reaction of NO with this complex are dominated by the lability of the coordinated water. Furthermore, the large and positive values of AVj and ASj point to a dissociative substitution mechanism as described in Eq. (6.43). 

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