Indium metal—carbon bonds

The thallium complexes show somewhat different electrochemical behavior, and reversible oxidations are observed for both n-alkyl and n-aryl thallium porphyrins, indicating that the oxidized complexes have a more stable metal—carbon bond than the gallium or indium analogs. Spectroelectrochemistry revealed that the first oxidation is porphyrin ring-centered. The first reduction is reversible and ring... 

Most of the studies on organo-gallium, indium, and thallium porphyrin complexes have focused on synthesis and properties of the complexes, and rather little attention has been devoted to reaction chemistry. Two areas which have received some attention are the insertion of small molecules (SO2 or CO2) into the metal—carbon bonds and photochemical metal—carbon bond cleavage. The... 

The interplanar separation of Rh(OEP)In(OEP) is 3.41 A compared to 3.26 A for [Ru(OEP)]2 As is also observed for the ruthenium dimer the In(OEP) core is twisted 21.8° relative to the Rh(OEP) group. Both the indium and rhodium atoms have an out-of-plane distance A4N which is the same as that previously reported for the corresponding o-bonded metal carbon complexes (given in Table 15 of part B V). A covalent radius of 1.36 A may be estimated from the metal-carbon bond length in In(TPP)(CH3). Similarly the covalent radius of the rhodium atom in Rh(OEP)(CH3) is equal to 1.26 A, giving a predicted covalent Rh-In distance of 2.62 A. This latter value is in good agreement with the observed value (2.584(2) A). In addition, the reactivity of the dimer... 

Inter-ring metal migrations, dynamic NMR studies, 1, 412 Intracyclic germanium-carbon bond formation large rings, 3, 706 small rings, 3, 703 Intramolecular Alder-ene reactions with metals, 10, 576 with palladium, 10, 568 with rhodium, 10, 575 with ruthenium, 10, 572 with transition metal catalysts, 10, 568 Intramolecular allylations, in cyclizations, with indium compounds, 9, 679... 

Garbometallation of carbon-carbon unsaturated bonds is an important synthetic method for the construction of complex molecules.277-281 An example of carboindation is described with tri(5-hexenyl)indium, prepared from di(5-hexenyl)mercury and indium metal, which is cyclized to a cyclopentylindium compound.282... 

The zinc-mediated Reformatsky reaction is one of the classical methods for carbon-carbon bond formation. To date, various main group metals and transition metals have been used for this reaction. Rieke s activated indium powder mediates readily the coupling of ethyl a-bromoacetate and a variety of carbonyl compounds yielding /3-hydroxy esters in good yields (Scheme 87).3 Later, commercially available indium powder has been found to be equally effective for the indium-based Reformatsky reaction in THF.28 This indium Reformatsky reaction is accelerated by ultrasound irradiation (Scheme 88).322,323 Indium(i) iodide also mediates the Reformatsky reaction of aldehydes and ketones to give /3-hydroxy esters, presumably via organoindium(m) diiodide (Scheme 89).27... 

Indium metal reduces the terminal triple bond of aryl propargyl ethers, amines, and esters in aqueous ethanol to produce the corresponding alkenyl compounds (Tab. 8.23) [119]. Indium metal in aqueous ethanohc ammonium chloride reduces the carbon-carbon double bond of activated conjugated alkenes such as a,a-dicya-no olefins, /faryleriories, and enone esters (Scheme 8.88) [120]. 

The indium-mediated Barbier reaction has certainly become one of the most popular reactions for creating a carbon-carbon bond under aqueous conditions and has led to spectacular developments in recent years. Compared to other metals, indium is resistant to oxidation, hydrolysis, and has a very low first ionization potential (5.79 eV, in contrast to the second one which is quite normal) which confers on it a remarkable reactivity in Barbier-type reactions. In 1991, Li and co-workers reported the first allylation of aldehydes and ketones mediated by indium in water without any additives or special activation [133]. In particular, the use of indium allowed reactions with acid-sensitive compounds [134] or the preparation of complex carbohydrates such as deaminated... 

Various metal-metal single o-bonded complexes have been obtained by the reaction of metal carbonyls with metal-carbon o-bonded porphyrins or by the reaction of metal carbonyl anions and chlorometalloporphyrins (Scheme 14). For example, the reaction of dimanganese carbonyl and methyl indium(III) porphyrin gives manganese pen-tacarbonyl indium porphyrin In(Por)Mn(CO)5. The same compound is isolated when chloroindium porphyrin is allowed to react with the manganese pentacarbonyl monoanion. Various iron, cobalt, tungsten, and molybdenum complexes have been prepared by these two methods. 

Qualitatively, most metal-mediated allylation reactions in aqueous medium display similar regio- and stereoselectivities. Such studies have been carried out most extensively on the indium-mediated allylations. For regioselectivities of the allylic moiety, both electronic and steric effects are important. Usually, the carbon-carbon bond formation occurs at the more substituted carbon of the allyl halide, irrespective of the position of halogen in the starting material (Eq. 4.28). However, the carbon-carbon bond forms at the less substituted carbon when the y-substituents of allyl halides are large enough (e.g. trimethylsilyl or tert-butyl) as shown by Chan and Isaac. 

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