Indium species

The effect of metal promoter species on the rate of carbonylation of [Ir(CO)2l3Me] was tested. Neutral ruthenium iodocarbonyl complexes such as [Ru(CO)3l2]2> [Ru(CO)4l2] or [Ru(CO)2l2]n were found to give substantial rate enhancements (by factors of 15-20 for a Ru Ir ratio of 1 13 at 93 °C, PhCl). Indium and gallium triiodides and zinc diiodide had comparable promotional effects. By contrast, addition of anionic ruthenium(II) species [Ru(CO)3I3] or [Ru(CO)2I4]2 did not lead to any appreciable promotion or inhibition. This behaviour indicates that the ability to accept an iodide ligand is a key property of the promoter. Indeed, it has been demonstrated that an iodide ligand can be transferred from [ Ir(C0)2l3Me] to neutral ruthenium or indium species [73,74],... 

A study of the species present in these solutions and the mechanism of the deposition has been presented [71]. Under the conditions of the depositions, the main solution indium species (in the absence of thioacetamide) are In-Cl (mainly [InCU] ) complex species. Only ca. 1% of the total In content is present as free In. No ln(OH)3 or hydroxy-complexes were calculated to be present if acetic acid was present (in the absence of acetic acid, the hydroxide could form). From a kinetic analysis of the deposition reaction, it was concluded that the deposition occurred by direct reaction between the thioacetamide and the chloro-indium complexes. It was noted that thioacetic acid was the main by-product and that no acetamide was detected (see 8ec. 3.2.1.3 for a description of the possible mechanisms and by-products of thioacetamide hydrolysis). Acetonitrile (CH3CN), a less common by-product, was also detected at the higher pH values (these depositions took place between a pH of 2 and 3) but not at the lower ones. 

Schweitzer and Anderson (125), working at a very low metal concentration, found the monomeric indium species InA3(HA)3 in the extraction with hexanoic acid in chloroform. This composition is in accord with that found in the decanoate extraction (145). 

The formal potentials of In(III)/In in the basic ionic liquids of 49.0 and 44.4 mol% AICI3 are reported as 1.009 and —1.096 V, respectively. A monovalent indium species, In(I), is not stable in this melt forming metallic In and InClj" as shown in the following disproportionation reaction ... 

The relative diastereoselectivity in the indium trichloride-mediated allylation with allylic stannanes in water is for the anti homoallylic alcohol [204]. The reactions are anti selective regardless of the geometry of the starting 2-butenylbro-mide. The in-situ-generated allylic indium species undergoes reaction with the... 

Stannanes and silanes may act as carbanion derivatives that can be activated with suitable Lewis adds. Thus, as shown by Cossy et al. [440], allylstannanes may be transmetalated with InCU to generate allylindium derivatives in situ. The latter can react with aldehydes to give mixtures of syn and anti adducts (with aromatic aldehydes and 2-buten-l-al). With aliphatic aldehydes, only the anti adducts are observed. The authors concluded that product mixtures were partly caused by the kinetic formation of a mixture of indium (Z)- and ( )-allyl esters prior to the condensation. They then allowed the indium species to equilibrate prior to the aldehyde addition and obtained mainly anti adducts (627, 628) (Scheme 130). 

The literature in this area is fairly sparse, presumably because of the ease of preparation of allyl- and propargylamines by nucleophilic amination. The reaction of allylindium species with aryl azides to give A -allylarylamines was mentioned earlier (Eq. 25). It has also been applied to the indium species derived from methyl 2-(bromomethyl)acrylate.269 The amination of alkylzirconium species mentioned above (Eq. 41) can also be applied to allenes (Eq. 51).116... 

A major improvement was realized with the use of indium, a metal with a very low first ionization potential (5.8 eV) which works without ultrasonic radiation even at room temperature [87]. As the zero-valent indium species is regenerated by either zinc, aluminum, or tin, a catalytic amount of indium trichloride together with zinc, aluminum [88], or tin [89] could be utilized in the allylation of carbonyl compounds in aqueous medium. The regeneration of indium after its use in an allylation process could be readily carried out by electrodeposition of the metal on an aluminum cathode [90], Compared with tin-mediated allylation in ethanol-water mixtures, the indium procedure is superior in terms of reactivity and selectivity. Indium-mediated allylation of pentoses and hexoses, which were however facilitated in dilute hydrochloric acid, produced fewer by-products and were more dia-stereoselective. The reactivity and the diastereoselectivity are compatible with a chelation-controlled reaction [84, 91]. Indeed, the methodology was used to prepare 3-deoxy-D-galacto-nonulosonic acid (KDN) [92, 93], N-acetylneuraminic acid [93, 94], and analogs [95],... 

As the zero-valent indium species is regenerated by either zinc or aluminum, a catalytic amount of InCls, together with either zinc or aluminum, could be utilized in the allylation of carbonyl compounds in tetrahydrofuran-water mixture. The presence of water was found to be effective in suppressing undesired side-reactions (Araki et al, 1992). 

In the area of nucleophilic acyl substitution using C-nucleophiles, Baba et al. found that the allylation of acid chlorides using allylic tin catalyzed by InCla stop at the allylketone product when the allylic tin compound is terminally substituted, otherwise for y-unsubstituted allylic tins, further allylation of the allylketone would occur [148]. Addition of PPh3 for y-unsubstituted allylic tin reactions would halt the allylation at the allylketone stage, but would inhibit reactions of y-substituted allylic tin (Figure 8.61). A mechanism was proposed involving transmetallation to form an allylic indium species followed by coordination of PPh3 with the indium center. 

Other frans-hydrometalation of alkynes includes the use of a combination of InCls and DIBAL to produce alkenyl indium species [43], and a Lewis acid catalyzed hydrogermylation of terminal/intemal alkynes (Fig. 19) [44]. In both cases, frans-hydrometalation was believed to account for the stereoselectivity of the reactions. 

In view of the above redox cycles. In-containing zeoUte catalysts prepared by RSSIE are obviously promising candidates for redox reactions, because of their fully reversible changes in the oxidation state of the indium species incorporated and stabiUzed in the zeolite matrices. 

Table 13.26 Literature thermodynamic data for indium species at 25 °C. ...

In an innovative expansion of the method to include aldehyde propargyla-tion, Marshall has documented the synthesis and use of chiral allenyl tin (169) [104, 111], zinc (174) [112], and indium (175) [113] reagents (Scheme 5.29) [106]. The allenyl zinc and indium species are believed to be formed in situ from chiral propargyl mesylates 172. Oxidative addition of Pd to... 

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