Complexes of Gallium

The colorless, crystalline tetramethylbis(/r-propynyl)digallium (XL) was prepared by the reaction of dimethylgallium chloride and sodium propynide 

Two different types of gallacarboranes with a closo structure have been reported in the literature. They can also be regarded as n complexes of a nido-carborane dianion and a RGa2+ center. 

In analogy to the synthesis of the aluminum compounds XXXVI and XXXVII the closo gallium carboranes XLIII and XLIV have been prepared (141), but crystal structures are not yet available. From NMR spectroscopic data it appears that they possess icosahedral structures as shown in Fig. 9. 

From solutions of GaCl2 in hot 1,3,5-trimethylbenzene the colorless crystalline bis(arene) complex [C6H3(CH3)3]2Ga+ GaCl4 (XLVI) has been isolated (158). The structural study reveals a bent sandwich structure for the cationic moiety, as indicated schematically in Fig. 9. The tetrachlorogallate tetrahedra are once more only weakly coordinated, this time via one chlorine atom each to the Ga(I) centers of two bis(arene)gallium units, forming a chainlike coordination polymer. The steric requirement of the mesityl ligands is 

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Metal-halogen stretching vibrations in coordination complexes of gallium, indium and thallium. A. J. Carty, Coord. Chem. Rev., 1969,4, 29-39 (32). 

Several other analytical procedures exist in which solvent extraction may be applied. Thus extraction has been used in a limited number of analyses with procedures such as (1) luminescence (fluorimetry), where, for example, the detection limit of rhodamine complexes of gallium or indium can be increased by extraction [28] (2) electron spin resonance using a spin-labelled extractant [29] and (3) mass spectrometry, where an organic extract of the analyte is evaporated onto pure AI2O3 before analysis [30]. 

Overall, the UV-visible, NMR, and electrochemical data for the range of O -bonded complexes of gallium, indium, and thallium porphyrins show that there is a trend from pure a -bonded character of the M—C bond in the alkyl complexes to the much more ionic character observed for the fluorophenyl and acetylide complexes. These more ionic complexes show NMR and UV-visible characteristics more like those of the ionic M(Por)Cl or M(Por)C104 complexes. ... 

A few studies of Schiff base complexes of gallium have been made.415,674 Frequencies v(Ga—O) have been located in the range 600-685 cm-1. Modes v(C=N) are almost unaffected by complexation. 

More recently, the synthesis of an amine-phenol complex of gallium(III) was described (Fig. 10). The antimalarial activities were in the micromolar range against the HB3 CQ-susceptible and Dd2 CQ-resistant strains. The authors proposed that the cytotoxic targeting properties of these kinds of metal complexes lie in the spatial orientation of substituents on the peripheral part of the molecule [98]. 

Kinetically stable complexes of gallium are being examined for use as imaging agents in diagnostic nuclear medicine... 

Other complexes of gallium have been more exhaustively studied. Gallium hydride, GaH3, forms with trimethylamine a 1 1 solid complex which melts at 69°C. and decomposes slowly even at room temperature (23), X-ray diffraction studies of the 1 1 complex show the presence of H3GaN(CH3)3 units with two molecules per unit cell. A coordination number of 4 for gallium is indicated (21). 

The sensitive and selective spectrophotometric methods involve extraction of ion-associates of the GaCU" ion with basic dyes (e.g., Rhodamine B). Methods based on ternary complexes of gallium with chelating triphenylmethane reagents (e.g., Eriochrome Cyanine R) and some surfactants are very sensitive but less selective. 

Gallium can also be determined with Methylene Blue (formula 48.1) [30]. A very sensitive method (e =2-10 ) is based on an extractable (toluene) ion associate of the anionic pyrocatechol complex of gallium and Brilliant Green [31]. 

Cationic Compiexes. Apart from the aqua ions and partially substituted species such as [GaCl(H20)5] +, cationic complexes of gallium halides with pyridine, bipyridine, or phenanthroline are known, for example, [GaCl2(phen)2]+ and [Ga(phen)3] +. Furthermore, given the steric hindrance about the gallium center in complexes formulated as GaX3(NH3) (X = Cl, n = 1, 3, 5, 6, 7, 14 X = Br, n = 1, 5, 7, 9, 14 X = I, n = 1, 5, 6, 7, 9, 13, 20), it is likely that where n is greater than 3 these are also cationic solvates. 

Mixed hydrido-alkyl complexes of gallium have been prepared, e.g. reactions (20)—(24), (M = Na or K R = Me or Et). The synthesis and properties of dimethylgallium tetrahydroborate have been examined, ... 

Field TB, McCourt JL, MeBryde WAE (1974) Composition and stability of iron and copper citrate complexes in aqueous solution. Can J Chem 52 3119-3124 Briggs TN, Stuehr JE (1975) Simultaneous potentiometrie determination of precise equivalent points and pK values of two- and three-pK systems. Anal Chem 47 1916-1920 Harris WR, Martell AE (1976) Aqueous complexes of gallium(III). Inoig Chem 15 713-720... 

Levin VI, Kodina GE, Novoselov VS (1977) Composition and stability of complexes of gallium and indium with citric acid. Koord Khim 3 1503-1505... 

Suslova, E.V., Kessler, V.G., Gohil, S., and Turova, N.Ya. (2007) Oxoethoxide chlorides - first representatives of oligonuclear alkoxide complexes of gallium penta- and dodecanuclear molecules. Eur. J. Inorg. Chem., 5182-5188. 

Metals of Valency Three and Higher.— The kinetics of the formation of complexes of gallium(iii), indium(iii), and thallium(iii) with semi-xylenol orange (5 shown in the form H3SXO ) in acid solution have been reported. The... 

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