Iron -hydrido

The first six entries in this section of Table X (entries 93-98) relate to attempted insertion reactions of fluoroalkenes or fluoroalkynes into Si-Mn or Si-Fe bonds. Even in the successful cases, yields are generally low, and in some instances (e.g., entry 94) MesSiF is lost from the insertion product to leave a fluoroalkenyl manganese carbonyl. In the case of the iron hydrido compound in entry 98, there is formal loss of hydrogen to give the binuclear derivative [CljSiFelCO). ... 

This chapter treats iron complexes with Fe-H bond(s). An H ligand on a transition metal is named in two ways, hydride and hydrido. The term hydrido is recommended to be used for hydrogen coordinating to all elements by lUPAC recommendations 2005 [1], However, in this chapter, the term hydride is used because it has been widely accepted and used in many scientific reports. 

Hydride species were also formed in the dehydrogenative coupling of hydrosilanes with DMF [45]. The catalytic system is applicable to tertiary silanes, which are known to be difficult to be converted into disiloxanes (Fig. 17). The catalytic reaction pathway involves the intermediacy of a hydrido(disilyl)iron complex... 

The reductive dehalogenation of haloalkanes has also been achieved in high yield using polymer supported hydridoiron tetracarbonyl anion (Table 11.15). In reactions where the structure of the alkyl group is such that anionic cleavage is not favoured, carbonylation of the intermediate alkyl(hydrido)iron complex produces an aldehyde (see Chapter 8) [3]. 

Nitroarenes are reduced to anilines (>85%) under the influence of metal carbonyl complexes. In a two-phase system, the complex hydridoiron complex [HFe,(CO)u]2-is produced from tri-iron dodecacarbonyl at the interface between the organic phase and the basic aqueous phase [7], The generation of the active hydridoiron complex is catalysed by a range of quaternary ammonium salts and an analogous hydrido-manganese complex is obtained from dimanganese decacarbonyl under similar conditions [8], Virtually no reduction occurs in the absence of the quaternary ammonium salt, and the reduction is also suppressed by the presence of carbon monoxide [9], In contrast, dicobalt octacarbonyl reacts with quaternary ammonium fluorides to form complexes which do not reduce nitroarenes. 

The second point relates to this as well as to your observation that the abstraction of hydrogen from water molecules is assisted by coordination of the water, particularly with Fe+2. The mechanism of ferrous oxidation by hydrogen atom has been a controversial question, and several mechanisms have been proposed. Among them are one suggested by Jortner, Czapski, Stein, and myself involving the addition of hydrogen atoms to the ferrous ion to form a hydrido iron complex analagous to CuH+—i.e.,... 

SF,MnO,Cft, Manganese(I), pentacarbonyl-(trifluoromethanesulfonato)-, 26 114 SF,OiCH, Methanesulfonic acid, trifluoro-iridium, manganese and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 SF,04P,PtC 4H , Platinum(II), hydrido-(methanol)bis(triethylphosphine)-irans-, trifluoromethanesulfonate, 26 135 SF,0 ReCs, Rhenium(I), pentacarbonyl-(trifluoromethanesulfonato)-, 26 115 SFe,OgC,H , Iron, nonacarbonyldihydrido- j.j-thiotri-, 26 244... 

It is deduced from infrared data (206) that iron pentacarbonyl reacts with bromine at — 80° C to form the cationic halogeno carbonyl [Fe(CO)sBr]+Br (206), and the covalent Br—CO—Fe(CO)4Br. From similar infrared data, however, it is concluded that the product is a seven-coordinate non-ionic complex Fe(CO)5Br2 (76) The reaction of Os(CO)3(PPh3)2 with hydrogen chloride produces a cationic hydrido carbonyl, which may be isolated, although it readily reverts to a neutral dichloride by attack of the associated chloride anion (52). 

In both compounds the iron atom geometries can be described as intermediate between octahedral and bicapped tetrahedral, but in the hydrido complex the H-Fe-H bond angle is 100°, whereas the Au-Fe-Au bond angle is only 73°. This smaller angle leads to an Au-Au distance of3.028(1) A, which is indicative of a weak interaction between the gold atoms. 

Reaction of Fe3(CO)12 with 3-pentyn-l-ol gives the hydrido cluster 4, formed by coupling of an allenylidene unit with a coordinated carbonyl ligand and methoxy group. In contrast, reaction with the isomeric alkyne 2-methyl-3-butyn-2-ol affords a binuclear iron complex.18 Treatment of Fe3(p3-S)2(CO)9 with Me3NO affords the vinylferrocene complex 5, whereas the similar reaction with Fe3(p3-Te)2(CO)9 gives no cluster products.19... 

A more favorable synthesis of salts of the iron, cobalt and nickel carbonyl anions, which were initially prepared by disproportionation reactions of Fe(CO)5, Co2(CO)8, and Ni(CO)4 with pyridine and other amines, was found by treatment of the neutral carbonyls with alkali in aqueous or alcoholic solutions. Careful studies by Hieber revealed that Fe(CO)5 as well as Fe3(CO)12 reacted with exactly four equivalents of hydroxide ions to give the corresponding dianionic iron carbonylates (Scheme 4.4). These dianions are relatively strong bases and readily accept a proton from a water molecule to give the monoanionic hydrido carbonylates [I IFe(CO)4] and [HFe3(CO)n], respectively [36]. The related carbonylates of cobalt and manganese, [Co(CO)4] and [Mn(CO)5], were obtained by a similar way as [Fe(CO)4]2 [25]. With regard to the mechanism of Hieber s Basenreaktion , the most plausible explanation is based on an initial nucleophilic attack by the hydroxide ion at the carbon atom of a CO... 

Scheme 4.4 Generation of iron carbonylates and hydrido carbonylates from neutral iron carbonyls according to Hieber s Basenreaktioif...

In deaerated methanolic solution, iron(II) hydrido complexes of the type [FeH(L)(dppe)2]+ (L = MeCN, MeCH2CN, CH,=CHCN, PhCN and p-MeC6H4CN) are reduced to [FeH(L)(dppe)2] by solvated electrons produced by y-radiolysis of the solvent.228 In pulsed radiolysis studies [FeH(L)dppe2] decays to five-coordinate [FeH(dppe)2] (half-life < 1 s). In continuous radiolysis however, [FeH(dppe)2] is not the final product and here as in its reaction with acids it is suspected that oxidative addition of a proton yields an unstable iron(III) dihydride which decom-... 

The electrochemical reduction of a series of cationic iron(II) hydrido complexes trans-[FeH(L)(dppe)2]+ (L = N2, C5H5N, PhCN, CH CHCN, MeCN, P(OMe)3, P(OEt)3, CO) has been shown to proceed via transient d1 iron(I) species which lose one of the neutral ligands. Further reduction of the resulting five-coordinate intermediates yields stable rf8 iron(O) anionic hydrides.233... 

This latter reaction is exemplified by the reaction of [Fe(PF3)5] with cyclopentadiene, which, in contrast with the analogous iron carbonyl system, gives the stable hydrido complex [Fe(f/5-C5H5)(PF3)2H]. 

A related reaction is that of the naphthyl hydrido derivative of iron(II), which forms the corresponding zero-valent PF3 iron complex 164) ... 

Hydrido(methyl)germyl iron complexes undergo elimination of methylgermanes to form four-membered cyclic Fe2Ge2 systems (equation The tendency for such con-... 

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