Iron, tetracarbonyl

Diaryl thioketones are converted by diiron enneacarbonyl into products of orthometallation.141 Oxidative or photochemically induced deligation of these complexes provides an unusual and valuable synthetic entry into compounds in the uncommon isobenzothiophene category142,151 (Scheme 84). Moreover, the photochemical procedure provides the novel complex, (tetracyanoethylene)tetracarbonyl iron. The orthometallated complexes (68) can also be used to prepare isobenzofurans (see Section IV,B,5). 

Although nickel tetracarbonyl, iron pentacarbonyl, and diiron enneacarbonyl were already prepared in the 1890s, more than three decades passed before the chemistry of transition metal carbonyls took off. Undoubtedly, some parts of the chemical community had recognized that compounds such as Ni(CO)4 and Fe(CO)5 deserved special attention, in particular due to the use of Ni(CO)4 for the production of pure metallic nickel. However, since the structure of those compounds was unknown, transition metal carbonyls remained, more or less, a curiosity. 

Insertion of isocyanide carbon atoms into the Cr—carbene bond of [(CO)5CrC(OMe)Me] gave aziridinylcarbene complexes (CIV), some reactions of which are summarized in Scheme 2 28, 198). Cyclic carbene groups (CV)-(CVIII), in which the carbene carbon atom is part of an aromatic six-electron Tr-system, have been reported to form pentacarbonyl chromium and tetracarbonyl iron complexes 383, 384). Related to carbene... 

Alkyl tetracarbonyl iron(O) reagents in solution decompose more rapidly with increasing concentration and temperature, especially above 0°. Carbon monoxide must be added without delay to convert this intermediate to the more stable acyl iron compound. 

The tetracarbonyl iron complex of methyl acrylate, methyl 2-chloroacrylate ° and methyl crotonate react in a similar fashion. Although the resulting jj -alkyliron complexes are stable (requiring treatment with trifluoroacetic acid followed by a oxidant to free the organic group from the iron), they are not well characterized. 

Recently, a method was described for the real-time measurement of growth rates and feedback control of three-dimensional laser assisted chemical vapor deposition [11]. This method allows the accurate reproduction of high quality films, fibers, and three-dimensional structures. High aspect ratio axisymmetric forms of desired shape and microstructure were grown from vapor phase precursors by this method. Three-dimensional rods, cones, hyperboloids, and spheroids of pyrolytic graphite, nickel, iron, and nickel-iron superalloys were obtained from ethylene, nickel tetracarbonyl, iron pentacarbonyl, and mixtures of nickel and iron carbonyls, respectively. 

The use of sonolytic activation of Fe2(CO)9 in an inert solvent has proved to be a general process in the synthesis of a large number of (Ti-allyl)tricarbonyliron lactone complexes and provides an alternative route to those already established in the literature. Diiron nonacarbonyl failed to react with alkenyl epoxide (over a period of up to two weeks) in the absence of ultrasonication. Sonication may aid the breakdown of the diiron nonacarbonyl allowing generation of the highly reactive, coordinatively unsaturated tetracarbonyl iron species which after initial complexation to the double bond of the alkenyl epoxide can form the lactone complex. other pathways cannot, however, be ruled out. 

Jt-Allyltricarbonyliron lactone complexe s are useful precursors for organic synthesis. They were first reported in 1964 [254] and have since been shown to be available from a variety of substrates [255]. For example, they may be prepared from alkenyl epoxides or various butenediols [256] and their derivatives by treatment with tetracarbonyl iron [257]. Work in our laboratories had shown that these were useful precursors for a wid5.,range of naturally occurring p and 5-lactones and lactams [258] (Scheme 123). 

C26H24PbS, Triphenyllead 2,6-dimethylthiophenolate, 45B, 811 C2 7H2iNPbS, (8-Mercaptoquinolinato-S)triphenyllead(IV), 46B, 750 C2 7H2iNSSn, (8-Mercaptoquinolinato-S)triphenyltin(IV), 46B, 750 C2 H26SSn, Triphenyltin 2,4,6-trimethylthiophenolate, 39B, 550 C2 aH2oFe208Sn2, Di-M bis(cyclopentadienyl)stannyl-bis(tetracarbonyl-iron), 41B, 808... 

ClftHiiFeNO, (N-Methyl-cinnamaldehyde-imine)-tetracarbonyl-iron,... 

Scheme 4-73. Reactions of neutral ri -alkene(tetracarbonyl)iron complexes with nucleophiles.

Cationic alkene-Fp complexes are rather stable and easier to handle than their neutral alkene(tetracarbonyl)iron congeners. Due to their positive charge, they are inert towards electrophiles and, thus, can be employed as protecting groups for olefins. Bromination and hydrogenation of other double bonds in the molecule leaves them unaffected. On the other hand they readily react with various nucleophiles such as enamines, enolates, silyl enol ethers, phosphanes, thiols, and amines to give alkyl-Fp... 

Cationic ri -allyl(tetracarbonyl)iron complexes are powerful electrophiles that react with nucleophiles primarily to T -alkene(tetracarbonyl)iron complexes. Those species are rather labile and decompose during workup to afford substituted alkenes. This methodology has been described for the first time by Pearson using organocadmium nucleophiles. Similarly, Ti -allyl(dicarbonyl)(nitrosyl)iron complexes, despite the lacking positive charge, also smoothly react with various nucleophiles. As... 

Cationic ri -allyl(tetracarbonyl)iron complexes can also be employed in electrophilic aromatic substitution reactions. This allylation reaction is limited to electron-rich arenes and heteroarenes. Unsymmetrically substituted allyl complexes react with good to excellent regioselectivity and excellent stereoselectivity (Scheme 4—87). ... 

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