Iron complexes cyclopentadienyl arenes

Decomplexation of some metal complexes calls for drastic conditions. This is true for (/7-arene)(/7-cyclopentadienyl)iron(II) hexafluorophosphates, [FeAr(Cp)][PF6] [54, 55]. Although their chemical decomplexation is known [55 a], the most widely used method is pyrolytic sublimation at high temperatures (>200 °C) [55 b]. To evaluate MW irradiation as the method of decomplexation of such iron complexes, Roberts et al. performed the reaction in the presence of graphite [54]. They discovered that the yield of the free ligand from the [Fe( -N-phenylcarbazole)( -Cp)][PF6] complex (43) depended on the kind (flakes or powder) and amount of graphite, and on the irradia-... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

The use of transition-metal arene complexes to facilitate nucleophilic aromatic substitution features in a route to derivatives of thiosalicylic acid and hence to thioxanthone. The cyclopentadienyl iron complex of 2-chlorobenzoic acid is converted into the benzamide prior to displacement of the chloride by thiophenoxide. Photolytic decom-plexation followed by directed remote metallation of the diaryl sulfide yielded the heterocycle (Scheme 207) <2000SL975>. 

Nesmeyanov, Volkenau et al. were the first to replace cyclopentadienyl with another ligand in ferrocene, preparing cyclopentadienyl-arene iron complexes by reaction of ferrocene with aromatic compounds in the presence of AICI3 255-259). 

Cationic arene cyclopentadienyl iron complexes were first isolated from the reaction of CpFe(CO)2Cl with arenes in the presence of AICI3 [80]. Subsequently, Nesmeyanov developed the ferrocene route (Scheme 9) and for most arenes this is more convenient and efficient and has become the standard synthesis for this class of compounds [81]. It has drawbacks in that it requires a stoichiometric... 

The substitution of the halogen (fluorine and chlorine) also occurs very easily in arene cyclopentadienyl iron complexes. 

It has been shown that boratabenzenes can provide the framework for a new family of stable, 19-electron iron-sandwich complexes. For example, treatment of (C6Me6)FeCp with MeBBr2 leads to insertion to furnish the corresponding r 6-boratabenzene adduct (Scheme 18).33 The structures, EPR spectra, and reactivity of these boratabenzene complexes are very similar to their well-studied (arene)Fe(cyclopentadienyl) precursors. The unpaired electron resides in an antibonding orbital that is largely metal based. 

Iridium nanoparticles, preparation, 12, 82 Iridium(III) O-ligated complexes, preparation, 7, 315 Iridium polyhydrides, preparation and characteristics, 7, 405 Iridium pyrrolyl derivatives, reactivity, 7, 282 Iridium tetrahydrides, characteristics, 7, 407-408 Iridium trihydrides, preparation, 7, 405 Iridium vinylidenes, synthesis and characteristics, 7, 352 Iridium xyliphos complexes, properties, 7, 442 Iridoids, via Pauson-Khand reaction, 11, 360 Iron(arene) (cyclopentadienyl) cations, preparation and reactivity, 6, 166... 

This type of sandwich complex, first reported with iron as the central metal, has now become widespread with ruthenium as well. Early routes to ruthenium complexes were modeled on iron chemistry, and used the AICI3-catalyzed exchange of a cyclopentadienyl ligand for an arene in ruthenocene, or reaction of CpRu(CO)2Cl with AlCb/arene. These methods are less successful with ruthenium than with iron, however, owing to the greater stability of ruthenocene. A mixture of arene, pentamethylcyclopentadiene, and RuCls in the Zn reduction method gives good yields of the mixed-sandwich cations. A... 

This resulted in a synthetic procedure, namely, the oxidation of alkyls attached to the arene or cyclopentadienyl ring of the 77-complexes to give carboxylic acids of the arene cyclopentadienyl iron series [346, 347, 351). 

Transition metal organometallic complexes like dicarbonyl cyclopentadienyl iron [128], tricarbonyl cyclopentadienyl manganese [129] and iron-arene complexes [130,131] have also been reported as photoinitiators for photochemical crosslinking of cyanate esters. Photosubstitution of carbonyl groups by -OCN during irradiation initiates the reaction in the former case whereas photochemical dissociation of arene triggers it in the latter system. 

Table 2 summarizes the mixed arene-arene and arene-ligand complexes prepared. w-Arene complexes of polymers are also listed. Iron and Ru with benzene or toluene yield t-arene complexes that can be isolated at low temperature. The (CgHg)2Ru species is stable to 0°C, whereas the CgHjCHj-Fe analog is stable to — 50°C. Thus, these compounds can be isolated for use as intermediates in other reactions, e.g., the addition of cyclopentadiene to the (benzene) Fe complex, where on warming hydrogen transfers to benzene to yield ( -cyclopentadienyl) ( -cyclohexa-dienyl)Fe ... 

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