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The Group IIIB (13) (p139)

The Group IIIB (13) (p139). Aluminum Gallium Indium Thallium. Introduction (p139). All are more metallic than boron, such as aluminum is the commonest metallic element in the earth’s crust. Each of the elements forms [M(H 2 O) 6 ] 3+

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The Group IIIB (13) (p139)

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  1. The Group IIIB (13) (p139) Aluminum Gallium Indium Thallium

  2. Introduction (p139) • All are more metallic than boron, such as aluminum is the commonest metallic element in the earth’s crust. Each of the elements forms [M(H2O)6]3+ • Practically, many of their compounds are on the borderline of ionic-covalent character: the florides are ionic, the other halides have more covalent character. Hydrolysis (as Lewis acid), melting point

  3. Introduction (p139) • All four elements give trivalent compounds, but the univalent state becomes increasingly important for Ga, In, and Tl. The Tl+ is well defined in solutions: Tl2SO4 • The main reason for the existence of the univalent state: the decreasing strengths of the bonds in MX3, and the subgroup tendency

  4. The elements (p140) • Preparation: electrolysis (over-valtage) Aluminum: Al2O3·nH2O (bauxite, n = 1-3) NaOH Al(OH)4–filtrate CO2 Al(OH)3·3H2O Al2O3 dehydration HF electrolyzed Na2CO3 800-1000 °C, Na3AlF6 Al(l) Na3AlF6

  5. The elements (p140) • Protection of Al (O2, H2O, X2, H+, OH–, …) On the surface: Al2O3, hard and tough film Method: Chemical oxidizing (passvation) Anodizing Destruction of the film: Scratching Mineral acids Amalgamation

  6. The elements (p140) • Ga, In, and Tl are similar as Al • Tl dissolves only slowly in H2SO4 and HCl, because the formed Tl(I) salts are only sparingly soluble. Tl, toxic • Ga, low melting point (302.78 K), high boining point (2676 K), as thermometer. GaAs, a semiconductor base material • Trivalent salts easily hydrolyzed

  7. The aqua ions, Oxo salts, and Aqueous Chemistry (p142) • [M(H2O)6]3+: halides, sulfates, nitrates and perchlorates Note: • Phosphates, sparingly soluble, partly hydrolysis, high viscosity • Alums: MAl(SO4)2·12H2O, Al can be replaced by transition metals from Ti to Co, also Ga, In, Rh, and Ir

  8. The aqua ions, Oxo salts, and Aqueous Chemistry (p142) • Hydrolysis of [M(H2O)6]3+: Ka1 in the order: Al (The smallest) < Ga > In < Tl (The largest), 1.12E-5 to 7E-2 Salts of strong acids: extensive hydrolysis Salts of weak acids: can’t exist in contact with water

  9. The aqua ions, Oxo salts, and Aqueous Chemistry (p143) • Hydroxides of Aluminum and Gallium are amphoteric, while those of Indium and Thallium are purely basic. • Polymerization: [Alm(OH)nOx]3m– n – 2x • pH 8 ~ 12: OH bridged polymer, Octahedral Al pH > 13, C < 1.5 M: tetrahedral Al(OH)4– pH > 13, C > 1.5 M: [(HO)3AlOAl(OH)3]2–

  10. Chemistry of Thallium (p143) • Thallium(III) carboxylates: Acetate and trifluoroacetate are useful in organic synthesis: a direct thallating agent, or an oxidant. Examples as follows: C6H6 C6H5Tl(OOCCF3)2 HOC6H4OH (O)C6H4(O) HOOCCF3 HOOCCF3 Dehydrogen reaction

  11. Chemistry of Thallium ( p146) • Two aspects about Tl(I) should be noted: • Anions can stabilize Tl(III) more than Tl(I), so E(Tl(III)/Tl(I) is sensitive to pH and occurring anion. Factors effecting stability of Complex: Z, r 2. Tl+ resembles K+ and Rb+, or Ag+, in some ways TlX Radius polarization Tl2O, Tl(OH), salts

  12. Oxides (p140) • Alumina: α-Al2O3,γ-Al2O3 Prepared over 1000 oC Stable and hard, as abrasive Resistant to hydration attack by acids Corundum Obtained by dehydration of hydrous oxides at low T (~ 450 oC). Readily absorbs water dissolves in acids Reactivity Alumina As solid materials in chromatograph

  13. Oxides (p140) NH3·H2O Al3+ AlO·OH boehmite Boining NaOH CO2 Al(OH)4– Al(OH)3 • Mixed oxides: • Containing traces of other metal ions (Cr3+, Fe3+, Ti4+, Fe2+), Ruby ,Blue Sapphire • MIIMIII2O4, spinal structure such as MgAl2O4,BeAl2O4,Na2Al2O4

  14. Halides (p141) • TlX3, not stable but TlF3, TlI3, rather TlI(I3) • Ionic, or ionic-covalent character • Structure: discrete dimer, even Al2(CH3)6 • Solubility in nonpolar solvents • As Lewis Acid, hence catalyst

  15. Hydrides (p144) • LiAlH4 and LiGaH4 reducing agents like LiBH4 • Both rapidly and often explosively hydrolyzed by water. Soluble in ether, which is the character of salts of Li. • LiGaH4 decomposes slowly even at 25 oC to LiH, Ga, H2

  16. Hydrides (p144) • Preparation: • 4 LiH + MCl3 LiMH4 + 3 LiCl • Na + Al + 2 H2 NaAlH4 • NaAlH4 + LiCl NaCl(s) + LiMH4 (C2H5)2O THF 150 oC, 2000 psi (C2H5)2O

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