Iron sandwich compounds with

Transition-Metal Metallacarboranes. The first demonstration of the insertion of a transition metal into an open face of a borane cage was with the iron sandwich compound [common-Fe(C2B9H11)12]2 [12541 -50-3] (188). This product is readily air-oxidized to [rt /W 0 -(C2B9Hn)2Fe]- ... 

The [3]-l,2-dicarbaundecahydroundecaborate(2—) ion, B9-C2Hii, has been found to form sandwich compounds with iron " and cobalt. Two synthetic procedures, one in non-aqueous and the other in aqueous media, have been developed. The procedure in nonaqueous media is general, whereas that in aqueous media can be used only to prepare complexes which are not decomposed by base. Both methods of preparation are... 

Interest in the metallocenes began in the 1950s when two independent groups (Pauson is often credited as the first) prepared ferrocene by reaction of iron II chloride with cyclopentadienyl magnesium bromide and by reaction of reduced iron with cyclo-pentadiene in the presence of potassium oxide. Ferrocene is a true sandwich compound with the iron resting between two planer and parallel cyclopendadiene groups. 

Irradiation of tricarbonyl(r(4-cyclobutadienc)iron(0) with ethyl 1//-azepine-l-carboxylate results in the formation of the novel sandwich compound (t 4-cyclobutadiene)[l-(ethoxycar-bonyl)-1 //-azepine]iron(0) (27).223... 

Carbazole will react with 1 or 2 mol of ferrocene in hot decalin in the presence of aluminium-aluminium chloride producing crystalline derivatives in which either one or both" of the benzene rings is linked to iron, 25 and 26, respectively. The sandwich compound 25 was deprotonated to 27 with sodamide in liquid ammonia. A chromium carbonyl complex 28... 

Dithiocarbamates, in Ru and Os half-sandwiches, 6, 493 Dithiocarbenes, Pt complexes, 8, 439 Dithiocarboxy ligands, in molybdenum carbonyls, 5, 447 Dithiolate-bridged compounds in dinuclear iron compounds with Fe-Fe bonds, 6, 238 as iron-only hydrogenase biomimetic models, 6, 239 Dithiolate diamides, with Zr(IV), 4, 784 Dithiolene—uranium complexes, synthesis and characterization, 4, 212 Ditopic receptors, characteristics, 12, 489 Ditungsten complexes, associated reactions, 5, 748 Divinyllead diacetates... 

While the mercury compound shows localized N—Hg bonds, the TADB-system (which is isoelectronic with cyclopentadiene) forms a low-spin complex with iron. This was the first identified example of a sandwich-compounds of a boron-nitrogen ring. The complex is prepared by adding an etheric solution of TADBLi to a suspension of FeCl2 in tetra-hydrofuran. 

The entire series of (CH)nPj n ions are also known. In a very bizarre reaction64 it was found that cocondensation of V atoms and an excess of Bu C=P formed the sandwich compound 10-XXXIX. With iron, there are compounds containing Cp Fe(C2Bu2P3) and Cp Fe(C3Bu3P2) either as such or in the former case having one P atom forming a donor bond to the Mo or W atom of an M(CO)5 moiety.65... 

Reacting the methyllithium adduct 108 (R =/-Bu, R = Me) with iron(ll) chloride produced two compounds, one of which was the deep red sandwich compound 111, the structure of which was determined by the X-ray method <20050M4216>. 

At low temperature and pressure, a gas phase reaction can occur between iron atoms and toluene. The product, a rather unstable sandwich compound, reacts with ethylene to give compound X. Compound X decomposes at room temperature to liberate ethylene at —20° it reacts with P(OCH3)3 to give Fe(toluene)[P(OCH3)3]2. Suggest a structure for compound X. (Reference U. Zenneck and W. Frank, Angew. Chem., Int. Ed., 1986,25, 831.)... 

Sandwich compounds have been reported from the reaction of bora-benzene anions with iron(II) chloride. 

The first transition element compound containing only carbocyclic rings as ligands was bis(ri5-cyclopentadienyl)iron, [Fe(r 5-C5H5)2], which has a sandwich structure with two parallel p5- or Ji-bonded rings. The recognition that this compound was amenable to electrophilic substitution, similar to the aromatic behaviour of benzene, led to the suggestion of the non-systematic name ferrocene and to similar names for other metallocenes . 

G. Wilkinson, The Iron Sandwich. A Recollection of the First Four Months, . 1. Organomet. Chem., 1975,100, 273. This article is a nice account of the history of the discovery of ferrocene. Wilkinson, along with E. O. Fischer, won the Nobel Prize in Chemistry for his pioneering work on sandwich compounds. 

Several sandwich complexes with cobalt have been described <83CB95l, 83ZN(B)485>. Structurally they differ from the iron compounds only by a slight shift of the cobalt atoms from the ring centers... 

Although the cyclopentadienyt group, C5H5, has long been known to form compounds with metal or metalloidal atoms, no such compound was considered noteworthy until the first cyclopentadienyl compound of a transition metal was reported in 1951. This compound was bis(pema/mptocyclopen-tadienyl)iron, (7 5-C5H5)2Fe, commonly called ferrocene. X-ray studies, as well as a variety of other physical and chemical evidence, showed that ferrocene has a sandwich structure (23-XII). The remarkable structure of this molecule as well as its extraordinary thermal stability (to above 500° C)... 

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