Heat gallium compounds

Potassium amidogaUate, K[Ga(NH2)4], is prepared by dissolving gallium in a solution of KOH in liquid ammonia. Heating this compound to 300 °C under vacuum removes two moles... 

SAFETY PROFILE Confirmed carcinogen. Mildly toxic by intraperitoneal route. Most arsenic compounds are poisons. Can react with steam, acids, and acid fumes to evolve the deadly poisonous arsine. Molten gaUium arsenide attacks quartz. When heated to decomposition it emits very toxic fumes of As. See also ARSENIC COMPOUNDS and GALLIUM COMPOUNDS. 

The sulphides M2S3 are all made by direct combination of the elements. But GaS is also known and has an unusual layer lattice containing Ga2 ions (Hahn and Frank, 1955). The nitride GaN,unreactive to water and acids, is made by heating gallium in ammonia at 1000° the corresponding indium compound is best made by heating (NH4)3lnFg. Both have the wurtzite lattice. 

Table tr.1-58 Heat capacity Cp and Debye temperature d of gallium compounds... 

The composition of low-volatility two-component compounds in the Ga-Se system as controlled using chemical transport reactions has been studied (Zavrazhnov et al. 2003). For long-term heat treatment of a low-volatility phase in the presence of a transport agent, the annealed phase composition was found to be determined only by the temperature and the nature of the sample. In the case of a two-temperature anneal of gallium selenides with added iodine, the sample composition ranges are presented as a function of the cold and hot zones temperatures. A scheme of their experimental arrangement is shown in Fig. 6.14. 

Alkane elimination was also observed upon heating of the adducts RaGa NH2-NR R" [4 to 7, Eq. (2)] in boiling toluene, which gave the hydrazides 15 to 18 in excellent yields [Eq. (6)] [17]. One compound (17) was characterized by a crystal structure determination. Similar gallium hydrazides were obtained directly at room temperature without the isolation of stable adducts when the phenylhydrazine derivatives H2N-N(H)CeH5 [18] and H2N-N(C6Hs)2 [17] were employed. The products (15 to 18) form dimers... 

Pyridine readily forms stable coordination compounds. Thus, boron, aluminum and gallium trihalides react at 0°C in an inert solvent to give 1 1 adducts (cf. 85). Steric factors are important, and a-substituents decrease the ease of reaction. This is illustrated by the heats of reaction of pyridine, 2-methylpyridine and 2,6-dimethylpyridine with boron trifluoride which are 101.3, 94.1 and 73.2 kJ mol-1, respectively. The marked decrease in exothermicity here should be contrasted with the small steric requirement of the proton as shown by the pA., values of substituted pyridines (see Section 3.2.1.3.4). 

A thermographic material with only one heat-sensitive component is prepared by reaction of an organometallic compound such as phenylmercury(II) nitrate with a thiourea derivative.230 The product is ball milled and coated in a binder such as poly(vinyl acetate). Other organometallic compounds disclosed are those of bismuth, tin, gallium and germanium combined with a variety of sulfur-containing compounds such as thioamides and xanthates. 

Gallium(III) bromide is a hygroscopic, white solid which sublimes readily and melts at 122.5° to a covalent, dimeric liquid. The solid is ionic and its electrical conductivity at the melting point is twenty-three times that of the liquid.5 The vapor pressure of the liquid at T°K is given by the equation log p(mm.) = 8.554 — 3129/T and the heat of dissociation of the dimer in the gas phase is 18.5 kcal./mol.3 At 125° the liquid has the following properties 5,6 density, 3.1076 dynamic viscosity, 2.780 c.p. surface tension, 34.8 dynes/cm. and specific conductivity, 7.2 X 10-7 ohm-1 cm.-1 Gallium(III) bromide readily hydrolyzes in water and forms addition compounds with ligands such as ammonia, pyridine, and phosphorus oxychloride. 

---