Greenwood & Earnshaw. Chapter 7. Aluminium, Gallium, Indium and Thallium. Observations. The Trihalides of Aluminum

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1 Greenwood & Earnshaw 2 nd Edition Chapter 7 uminium, Gallium, Indium and Thallium Observations uminum is the most common metal, 8.% wt. of the earth s crust. Ga, In, are relatively rare. uminum is monoisotopic, excellent heat and electrical conductor. Gallium has anomalous melting point (but not boiling point) and anisotropic electrical resistivity: a 17.5, b 8.20, c 55.; liquid is 25.8 F ohm-cm. Thallium has a very stable oxidation state of one and is very electropositive, corrodes in moist air. I : III oxidative equilibria dominates its chemistry. The Trihalides of uminum polymeric solids, CN = 6, µ X dimeric CN = 4, 2 µ X alides once hydrated cannot be dehydrated. F alone does not form a hexahydrate. Cl 2 O [( 2 O) 6 ] + Cl- heat O(O)C 2 O + Cl 2 O F F Cn 2 O n = 1,, 9 the affinity of for F O heat 2 O 1

2 Complex alides Cryolite Structure F + NaF Na F 6 uminum Smelting Synthetic cryolite has the perovskite structure (CaTiO ) a face-centered cubic structure. No F 6 - ions occur. The is not clearly ionic since the Na-F and -F distances are nearly equal. l occupy octahedral sites; 1/ Na occupy octahedral sites, 2/ occupy 12 coordinate sites. Trihalides of Ga, In, & Complex alides The trichloride of is important as Friedal Crafts & isomerization Catylist. The trihalides of Ga resemble those of with some structural differences. The trihalides become less stable as one goes down the group. 10.9E Cl pm Other adducts vary GaCl 4 - T Cl In Cl between sq. pyd. & InCl d InCl 2- trig. bipyd. geometry pm Cl Cl square pyramidal The trihalides of are chemically quite distinct from the rest of the group. 2O F (O) + F NaF 4 Fluorite Str. mp d 550 C hydrolyses rapidly Na F 6 Cryolite Str. [ 2 Cl 9 ] - Two regular TiCl 6 octahedra sharing a common face. Ga(II) ~ In(II) Cl Cl Cl 2- vs. Ga(I)Ga(III) Ga Ga Cl Cl vs Cl Cl Ga Ga (I) (III) Ga+[GaCl4]- Cl Cl I is I but I 4 is (III); 2 I 4 is + - I 4 Acidity of [M( 2 O) 6 ] + ydrates, ydroxides and Oxides M Ga In * pk a * Needs "non-coordinating anion" (O) (O) Ga(O) In(O) O Acidic Amphoteric asic Strongly asic ~KO ~100 C atm 2O C ~100 C MO(O) layer lattice ~150 C InO(O) ~Rutile Str. 2 O black platelets ~1000 C M 2 O In 2 O 2 O structurally asic very complex O - See p 24 text 2 (SiO ) SiO + 2 CaO 2 O Acid Ca(O ase 2 ) 2 Oxide Acceptor Oxide Donor - O 2 2

3 Important uminum Oxides α-umina 2 O Corundum, Sapphire including very strong optical glass, Saffil fibres. γ-umina 2 O Activated alumina, a defect spinel structure. Sodium-β-alumina Na 11 O 17 -Na 2 2 O a solid electrolyte & Na + conductor, see Na/S battery applications, p 678 text. Tricalcium uminate Ca 2 O 6 Principal ingredient of Portland Cement. ( 4 ) N(C ) Complex Metal ydrides 2Me 6 N(C ) EC C fluxional ydrides:, Ga, In, & + /2 2 no reaction 4 Cl + Li 4 4 ( 2 O) n + LiCl benzene α- has 6 O h c-2e µ-'s reflux 6 d - = 24 pm, 6 d - = 445 pm, p = 141E, no - bonding. 4 Td EC 2 N(C ) (C ) N N(C ) LiGa 4 + Me N@Cl F Ga ydrides of In, too unstable to isolate Viscous liq. LiM 4 M = Ga In T mp -15EC T dec ~25EC EC T dec = 80E 100E 50E OE

4 , Ga, In, & -- kyls & ydrides + / R R C C 2 cf. ydroboration dimeric dimeric ineffective C C (C ) 2 C C 2 100EC 2 [C cat. amts. 2 C(C ) 2 ] [C 2 C(C ) 2 ] monomeric 200 atm 2 (C 2 C(C ) Na (C ) CC 2 ) [C 2 C(C ) 2 ] 2- mp 40EC, diamagnetic X + 2 RMgX R R + X- linear cation, isoelectronic with R2g R = Me, soluble and stable in water. uminum kyls The Growth Reaction 2C C 2 150EC 100 atm 2 C 2 C 2 2C C 2 150EC 100 atm (C 2 C 2 ) x (C 2 C 2 ) y (C 2 C 2 ) z 2 C C 2 C 2 C 2 2 C C 2 C 2 C 2 C 2 C 2 2 C C 2 C 2 C 2 etc C 2 C 2 C 2 C 2 C 2 C 2 uminum kyls Ziegler-Natta Catalysis TiCl Classical Mechanism: alkane solvent Ti(III) n Cl -n brown suspension L n Ti- 2 C C 2 2 C C 2 L n Ti L n Ti 2 C C 2 L n Ti C 2 C 2 2 C C 2 C 2 C c. C 2 C 2 C 2 C 2 or L n Ti L n Ti C 2 C C 2 C 2 L n Ti C2C 2 C C 2 L n Ti C 2 C 2 C 2 C L n Ti C 2 C C 2 C 2 2 C C 2 C 2 C 2 L n Ti C 2 C 2 C C 2 2 C C 2 2 C C 2 2 C C 2 4

5 uminum kyls Ziegler-Natta Catalysis Classical mechanism requires chain transfer of an ever increasing length chain, entropy consideration as polymer chains become very long. The concerted pathway was invoked to counter the entropy troubles above. Polypropylene is only head-to-tail, most valuable polymer produced by Z-N catalysis. The methyl groups alternate along the chain. Reactivity: terminal > geminal > internal olefins. Only homopolymerization feasible. Some Interesting Organometallics 241 pm O (aq) + C 5 6 Trialkyl derivatives of Ga, In, are all monomeric. Those of Ga & tend to be liquids or low mp. gas phase crystalline phase Indium compound has similar structure din-ring = 285 & 09 pm; pin 128E; pring 177E + C Ga C C C C C Ga r r Ga r r C C C In C C C O + O Me O Me O O + 5

Greenwood & Earnshaw. Chapter 7. Aluminium, Gallium, Indium and Thallium

Greenwood & Earnshaw. Chapter 7. Aluminium, Gallium, Indium and Thallium Greenwood & Earnshaw 2 nd Edition Chapter 7 uminium, Gallium, Indium and Thallium Observations uminum is the most common metal, 8.3% wt. of the earth s crust. Ga, In, Tl are relatively rare. uminum is