Indium metal halides

Preparative hazard See Mercury(II) bromide Indium See other METAL HALIDES... 

The coordination chemistry of indium(I) received little or no attention for many years, largely no doubt because of the lack of suitable starting materials. The indium(I) halides can be easily prepared,1 but are intractable materials which readily undergo hydrolysis and disproportionation (but see Section 25.2.2.1). The only known organoindium(I) compounds are the cyclopentadienyl and methycyclopentadienyl derivatives,8 and the former has proven a useful starting point for some synthetic work. Electrochemical methods have been used either to reduce higher states, or to oxidize the metal in the presence of suitable ligands, in order to produce indium(I) species. 

A number of reactivity studies have been performed on 6 and 8 and indicate a strongly polar (if not ionic) Mn—E bond Mn "—E,+ (E = In, Tl). Thus heterolytic bond dissociation occurs in polar ligating solvents such as MeCN or DMF, and halogens, hydrogen halides, and alkyl halides readily add across the metal-metal bond in a manner consistent with the polarity described above (13,13a,18). In the thallium example, however, the reactions are generally more complicated and result in T1(I) salts [e.g., Eq. (3)], and metal exchange reactions are also more facile, e.g., the synthesis of 6 from 8 and indium metal. In general, therefore, the chemistry of 6 and 8 is consistent with predominantly ionic behavior. 

All the above complexes, 9-12, are isolated from reactions involving gallium or indium metal and [Mn2(CO)10] or [Re2(CO)10] in an autoclave, although 11 has also been obtained by thermolysis of 6. Some details on the reactivity of 11 toward phosphonium halides (23) have been reported and indicate formation of the halo-indium complexes [PPh4]2[Mn2(CO)8 /j-lnX2 2]. A higher nuclearity cluster has also been obtained in the reaction of [Re2(CO)10] with indium metal, viz. [Re4(CO)12 /i3-InRe(CO)5 4], 13 (24,24a). This consists of a central tetrahedral Re4(CO)12 core with each face capped by an InRe(CO)s fragment as shown in Fig. 4. 

A three-component reaction based on the umpolung of re-allylpalladium (II) complexes indium metal was reported by Grigg and co-workers (Scheme 8.31) [74]. In this reaction, the electrophilic nature of the n-allyl palladium species generated from aryl halides and allenes is reversed by transmetallation with indium metal. The resultant nucleophilic allylindium reagent subsequently adds to the third component - aldehyde [75] or imine [76] - to give the corresponding homo-allylic alcohol 64 or amine 65 respectively. 

The most widely used preparative method of allylindium(m) or propargylindium(lll) compounds is the oxidative addition of metallic indium or indium(l) halides to allylic or propargyl substrates.4 26 27 Allylic bromides and iodides serve as good allylic sources without any other activation. In the case of allylic chlorides, a proper additive such as lithium iodide is required to promote the oxidative addition. Allylic indium compounds prepared by oxidative addition of metallic indium are considered to exist as the sesquihalide structure (allyl jImXj), which has been... 

The coupling reaction of a-keto esters with allyl, propargyl, and allenyl halides using indium metal in aqueous solvents affords a-hydroxy-y,<5-unsaturated esters (Equation (28)).197,198 1,3-Dicarbonyl compounds undergo efficient carbonyl allylation reactions in an aqueous medium through a Barbier-type reaction (Equation (29)). The reaction is general and a variety of 1,3-dicarbonyls has been alkylated using allyl bromide or allyl chloride in conjunction with indium.199... 

Indium-mediated allylation of cyclic and acyclic acid anhydrides gives w-diallyl esters.203,204 Examples are shown in Scheme 48 the allylation of succinic anhydride or phthalic anhydride with allyl bromide in DMF in the presence of indium metal results in the formation of diallylbutenolides or diallylphthalides. In contrast, monoallylated hydroxy esters are formed exclusively with y-substituted allylic halides. 

Treatment of tethered alkyne-allyl halides with indium metal in halogenated solvents affords carbocyclic vinyl halides via a novel atom-transfer reaction. The reactions are operationally facile and proceed smoothly at room temperature even with sub-stoichiometric quantities of indium. Use of a halogenated solvent containing a different... 

Indium (I) halides can be prepared by dissolving an excess of indium in hydrohalide acid or reduction of trUialides with metal. The structures of the bromides have been... 

A mixed indium hydride halide complex, (l) InH2Cl (29) has been prepared from the 1 1 reaction of [InH2Cl(NMe3) ] with carbene (1) (R = Mes, R = H), as shown in Scheme iP The structure of (29) is monomeric with the geometry at the In center close to tetrahedral. The In-C distance (2.244(6) A) is similar to those observed in (28) (2.200(7) A) and (25) (2.253(5) A). A related mixed gallium hydride iodide complex (1) GaH2l (30) has been isolated from the reaction of (26) with GaT, with concomitant deposition of galhum metal. Complex (30) is isostructural with the related indium complex (29) and has a Ga-C bond distance of 2.022(4) A. 

Vinyl halides add to allylic amines in the presence of Ni(cod)2 where cod=l, 5-cyclooctodine, followed by reduction with sodium borohydride. Aryl iodides add to alkynes using a platinum complex in conjunction with a palladium catalyst. A palladium catalyst has been used alone for the same purpose, and the intramolecular addition of a arene to an aUcene was accomplished with a palladium or a GaCl3 catalyst, " AUcyl iodides add intramolecularly to aUcenes with a titanium catalyst, or to alkynes using indium metal and additives. The latter cyclization of aryl iodides to alkenes was accomplished with indium and iodine or with Sml2. " ... 

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