Binary Carbonyl-Iron Complexes

Pentacarbonyliron is a stable 18-electron complex of trigonal-bipyramidal geometry and represents the primary source of most organoiron complexes. Nonacarbonyldiiron is prepared in a photolytic reaction from pentacarbonyliron. Dodecacarbonyltriiron can be obtained from nonacarbonyldiiron by a thermal reaction. Both, nonacarbonyldiiron and dodecacarbonyltriiron, contain metal-metal bonds. They are slowly degraded to give pyrophoric iron and therefore should be handled with care. 

Iron carbonyls have been used in stoichiometric and catalytic amounts for a variety of transformations in organic synthesis. For example, the isomerization of 1,4-dienes to 1,3-dienes by formation of tricarbonyl(ri4-l,3-diene)iron complexes and subsequent oxidative demetallation has been applied to the synthesis of 12-prostaglandin PGC2 [10], The photochemically induced double bond isomerization of allyl alcohols to aldehydes [11] and allylamines to enamines [12,13] can be carried out with catalytic amounts of iron carbonyls (see Section 1.4.3). 

The reducing ability of iron(0) complexes has been exploited for functional group interconversion, for example reduction of aromatic nitro compounds to amines by dodecacarbonyltriiron [17]. 

The iron-mediated [2 + 2 + 1]-cycloaddition to cyclopentadienones has been successfully applied to the synthesis of corannulene [24] and the yohimbane alkaloid ( )-demethoxycarbonyldihydrogambirtannine [25]. A [2 + 2 + l]-cydoaddition of an alkene, an alkyne and carbon monoxide mediated by pentacarbonyliron, related to the well-known Pauson-Khand reaction [26], has also been described to afford cyclopentenones [27]. 

In the presence of an excess of a primary amine, this reaction has been applied to the synthesis of cyclic imides [29]. 

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The organometallic chemistry of the first-row transition metals generally starts with the binary metal carbonyl organometallic complexes. Noncarbonyl organometallic complexes starting with other easily accessible binary compounds provide entries to a broader spectrum of complexes. In this context, we describe the synthesis of the mixed sandwich complex (tj5-pentamethylcyclopentadienyl) ( j5-cyclopentadienyl) iron as an example of the synthetic utility of the solution-stable derivative (>j5-pentamethyl-cyclopentadienyl) (2,4-pentanedionate) iron. 

A very pronounced synergistic effect is found for binary ruthenium-iron carbonyl catalysts in the water-gas shift reaction. Both mixed ruthenium-iron clusters and mixtures of ruthenium clusters with iron complexes are considerably more active in basic solutions. Whereas the water-gas shift activity (moles of H2 per mole of complex per day) of alkaline aqueous ethoxyethanol solutions of Ru3(CO)12 and Fe(CO)j is... 

It is also convenient to include here the dithiolene group of complexes, as well as the oxidation states iron(I), iron(IV), and iron(VI). The iron(IV) oxidation state also occurs in oxide systems such as BaFeOj, but these will be discussed separately in Chapter 10. Covalent diamagnetic complexes such as carbonyls are included in Chapter 9 the oxidation state of iron in these complexes spans both positive and negative values and includes iron(0) as in the binary carbonyls themselves. 

Iridium(V) complexes, 1158 fluorides, 1158 Iridium(VI) complexes, 1158 Iron complexes acetonitrile, 1210 analysis, 1180, biological systems, 1180 coordination geometries, 1183 coordination numbers, 1182-1187 dinitrosyldicarbonyl, 1188 Mdssbauer spectroscopy, 1181 nitric oxide, 1187-1195 nitrosyls binary, 1188 bis(dithiolene), 1193 carbonyl, 1188 dithiocarbamates, 1192 halides, 1193 iodide, 1193... 

Within this context, the present article concentrates on transition metal cluster complexes of cobalt, iron and manganese with mixed chalcogen/carbonyl ligand spheres obtained by reaction of simple binary metal carbonyls with alkali-metal sulfides, alkali-metal thiolates or transition-metal thiolate complexes and their selenium or tellurium counterparts. 

Treatment of the pentairon cluster, [Fe5(/xs-G)(GO)i4] 71, with bipy causes a contraction of the cluster core to afford the tetrairon complex, [Fe(bipy)3][Fe4(/X4-G)(GO)i2(/4-H)]2 ([Fe(bipy)3] " (70 )2), in contrast to the reactions of the binary iron carbonyls, which result in substitution of two GO ligands by bipy. ... 

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