Iron, hydrido-, complexes

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. 

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]. 

Hydrido complexes, gold-osmium, 27 209 iridium, 26 117, 27 19 iron, 26 244, 27 168 iron-tungsten, 26 336 manganese, 26 226 mercury-molybdenum-ruthenium,... 

Usually the C-0 single bond in esters is cleaved at the acyl-0 bond, whereas examples of cleavage at the other point in esters have been reported. An electron-rich iron(O) complex produced on reductive elimination of naphthalene from a hydrido(naphthyl)iron complex undergoes oxidative addition reaction with methyl benzoate to give a methyliron benzoate complex (Eq. 22) [63]. 

Iron(II)-hydrido complexes containing organonitrile ligands of the form [FeH(L)(dpe)2] [dpe = l,2-bis(diphenylphosphino)ethane L = CHjCN, etc.] are reduced by the solvated electron in methanol the FeH(L)(dpe)j product rearranges, losing L to give the known FeH(dpe)2 complex (k = 10 - 10 s with CHj being fastest)" . ... 

M. Aresta, P. Giatmoccaro, M. Rossi, A. Sacco (1971). Inorg. Chim. Acta, 5, 115-118. Hydrido complexes of iron(IV) and iron(II). 

It should be noted that this mechanism explains the acid-catalyzed labilization of Fe(CO)5 (9) and the preferential exchange of three CO groups in (Ph3P)Fe(CO)4 in the presence of strong acids (10). Such iron(O) complexes apparently do not form stable adducts with proton acids but are in equilibrium with small amounts of cationic hydrido complexes. 

A possible catalytic cycle for the hydrogenation of CO2 to formate catalysed by the iron pincer complex 30 is as follows (Fig. 15) (1) Formation of the hydrido-formato complex 31 by direct electrophilic attack of CO2 on the rran -dihydride 30,... 

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