Complexes of indium

Dimethylpropynylindium (XLVIII) can be prepared by the reaction of dimethylindium chloride or bromide with sodium propynide as a colorless, crystalline substance 148). Whereas indium trimethyl is monomeric in benzene, the alkynyl compound is dimeric, but only sparingly soluble in this and other aprotic noncoordinating solvents. Improved solubility has been observed in diethyl ether due to the formation of a weak adduct 148). According to crystallographic data 148), compound XLVIII can be regarded as a coordination polymer in the solid state, as indicated in Fig. 10. The axial positions on the trigonal bipyramidal coordination polyhedron of each 

As mentioned earlier, cyclopentadienylindium(I) (L) was prepared nearly 30 years ago (160) as a pale yellow compound, sublimable in a high vacuum. In a later publication, Tuck and Poland (161) suggested the reaction sequence in Eqs. (9) and (10) for the synthesis of L. The thermal decomposition of 

In (C5H5)3 to L in vacuo above 100°C was confirmed by these authors, and the compound InC5H4(CH3) was obtained in a similar way (161). The preparation of L by condensation of indium vapor onto a matrix of C5H6 at 77 K was subsequently reported (169). 

The extensive controversy in the literature concerning the bonding in cyclopentadienylindium is summarized in a recent paper by Eisenstein et al. (153), which also contains a theoretical analysis of the bonding in other monomeric and polymeric C5H5M compounds. It is suggested that the 

InCl3 + 3 NaC5H5 - In(C5H5)3 + 3 NaCI In(C5H5)3 - InC5H5(L) + C10H10 

---

Biscarbene complexes of indium(III) halides can be isolated from the reaction of two equivalents of l,3-diisopropyl-4,5-dimethylimida-... 

There is a large temperature variation of solubility for the tris-dmpp complex of indium (143) but a much smaller variation for tris(malto-lato)aluminum (242) in aqueous solution. The solubility of the former increases by a factor of 3.5, of the latter by only 1.3 times, on raising the temperature from 298 to 310 K, i.e., from the standard 25°C to the physiological 37°C. The enthalpy of solution of Al(malt)3 in water is 23kJmol , but is medium-dependent, rising to 56kJmol in 80% methanol. 

The conventional preparative routes to anionic, neutral, or cationic complexes of indium start with the metal, which is dissolved in a suitable mineral acid to give a solution from which hydrated salts can be obtained by evaporation. These hydrates react with a variety of neutral or anionic ligands in nonaqueous solvents, and a wide range of indium(III) complexes have been prepared in this manner.1 Alternatively, the direct high-temperature oxidation of the metal by halogens yields the anhydrous trihalides, which are again convenient starting materials in synthetic work. In the former case, the initial oxidation of the metal is followed by isolation, solution reaction, precipitation, and recrystallization. 

The syntheses described below allow such a cycle of operations to be circumvented. As reported previously,2 the electrochemical oxidation of indium metal at room temperature in an organic solvent system yields neutral, anionic, or cationic complexes of indium(III) within 2-3 hours, usually in good crystalline form. These syntheses are significantly quicker and more convenient than the procedures used in this laboratory in previous work. 

The chemistry of indium complexes of aU types in metal oxidation states lower than +3 has been comprehensively reviewed. Few lower oxidation state mononuclear amido complexes of indium are well characterized, however, and no structure has been reported for an In(I) amide. The compound In N(SiMe3)2 n. which is unstable, " has been characterized NMR spectroscopy but its structure is unknown. The structures of several In(I) complexes, related to amides but outside our current scope, have been described. Like its aluminium and gallium counterparts, the p-diketuninate derivative [ In N(Dipp)C(Me) 2CH] has been characterized, as has the closely related species [ In N(Dipp)C(CF3) 2CH]. ° These feature V-shaped, two-coordination at the metal. The less bulky [(In N(Mes)C(Me) 2-CH)2] ° and 15-2.6-.Vlc,)( (Me) i are dimeric with long In In bonds of... 

The earlier discussion of complexes of indium(III) with nitrogen ligands emphasized the importance of six-coordination, and in keeping with this, XH and U5In NMR studies have identified [In(H20)6]3+ as the cation in aqueous solutions of perchloric acid.103,104 Confirmatory evidence has been obtained from dilatometric105 and X-ray diffraction106 methods. Proton... 

The weak complexing of indium(III) with chlorate, bromate and iodate has been studied, and stability constants reported, but no preparative work has been done. Perchlorate ion does not complex with indium(III).9... 

A series of earlier papers on complexes of indium(III) with porphyrins,265 and phthalocyanines266-268 has been summarized earlier.7 The structures InLX (L = substituted porphyrin X = Cl, OAc, OPh) imply a square pyramidal stereochemistry with the indium atom situated above the ligand N4 system, and this has been confirmed by X-ray crystallography for X = C1269 and X = Me,270 but for X = MeOS02, the indium atom is in the plane of the four nitrogen atoms.271 A number of Schiff base derivatives have recently been described.272... 

Simple preparations of IiiL3(C104)3 and In(terpy)2(C104)3 are known (140, 669). All three are normal six-coordinate complexes of indium(III). The compounds In(bipy)3X3 (X = Cl, Br, or I) have also been obtained... 

Several periodato complexes of indium(III) have been obtained by using In(N03)3 and HsIOg. At pH < 1, a crystalline product H33l2ln034 forms. At higher pH, insoluble, amorphous material of composition In5(I0g)3 H20 and H3ln4(I06)3 H20 was produced. 

Transition-metal complexes of indium and indium adducts are available.Structures, bonding, reactivity, and their materials-related applications are of current interest in the early 2000s. 

The bromide complex of indium gives extractable ion-associates with the xanthene basic dyes Rhodamine B [49] and triphenylmethane dyes. Brilliant Green [50,51], and Crystal Violet [52], extractable into non-polar solvents. The related dye. Malachite Green, has been used to form an associate with tetra-iodoindate, extractable with benzene, hexane, and CCI4 [53]. 

While numerous homoscorpionate complexes of indium have been previously reported,578 in the last period only a limited number of papers appeared. The reaction between [InCl2(Tp )(NCMe)] and (L = cyclopentadienyl)-tris(diorganylphosphi(ni)to-P)cobaltate(l-),... 

Green, J.H., Kumar, R., Seudeal, N. and Tuck, D.G. (1989) The direct electrochemical synthesis of alkyl and aryl thiolato complexes of indium and thallium , Inorg. Chem., 28, 123-127. 

Addition of six allylindium reagents to 2- and 3-pyridinecarboxaldehyde, and to glyoxylic acid (OHCCO2H), has been studied in water. " The stereoselectivity crosses over between the pyridine aldehyde isomers, which provides evidence for intramolecular complexation of indium by the pyridine nitrogen in the 2-position. The chelation ability of the 2-aldehyde is also compared to that of glyoxalic acid. 

Spec determination of the ternary complex of indium with haematoxylin or its oxidized form in the presence of cationic, anionic and non-ionic surfactants such... 

---