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Chapter 16 16 Elements

Physical Properties The elements Halides, oxohalides, , salts of oxoacids sulfides, polysulfides, polyselenides, polytellurides Compounds of and selenium with

1 • Dioxygen makes up 21% of the ’s and 47% of the Earth’s is composed of O-containing compounds (, , silica, ). • Sulfur occurs around volcanoes and hot springs,

fool’s (FeS 2), and other . • Selenium and are relatively rare and occur in only a few minerals • is omitted because its abundance is only 3 × 10 −7 ppb, giving a negative number on the log scale.

Relative abundances of the group 16 elements in the Earth’s crust

Production of sulfur in the US from 1980 to 2008

2 Uses of sulfur and sulfuric

3 ∆ o Given the fH (Na 2O,s) = -414 kJ/mol, determine the + 2- enthalpy change for the process: 2Na (g) + O (g) Na 2O(s)

Hint: Create an appropriate Born-Haber cycle and look up the necessary values for each of the steps.

∆ o 2 aH (Na) 2Na (s) + ½ O 2(g) 2Na (g) + O (g) ∆ o aH (O)

∆ o fH (Na 2O,s) ∆ o 2 IE (Na) EA H 1(O) 1 ∆ o EA H 2(O)

∆ Ho(Na O,s) lattice 2 + 2- Na 2O (s) 2Na (g) + O (g)

4 of oxygen

MnO 2 or Pt catalyst 2H 2O2 O2 + 2H 2O

∆, MnO 2 catalyst 2KClO 3 3O 2 + 2KCl

+ - 2- Describe bonding in [O 2] , O 2, [O 2] , [O 2] using MO theory.

+ - O2 + PtF 6 [O 2] [PtF 6]

+ - 2O 2F2 + 2BF 3 2[O 2] [BF 4] + F 2

Chemistry of and ∆ o -1 3/2 O 2(g) → O3(g) fH (O 3,g,298 K) = +142.7 kJ mol + - o O3(g) + 2H (g) + 2e ⇌ O2(g) + H 2O(l) E = +2.07 V − The structures of O 3 and [O 3] , and contributing resonance structures in O 3. − • The O O in O 3 is taken to be 3/2.

2KOH + 5O 3 2KO 3 + 5O 2 + H 2O (Ozonide salts)

Phosphite ozonide

5 Sulfur: allotropes

S6 S7 S8

catena -S

S8 + 24F 2 → 8SF 6 S8 + 4Cl 2 → 4S 2Cl 2 S8 + 4Br 2 → 4S 2Br 2

SF 6

2+ structure of [S 2I4]

6 2- Polysulfides, [S x] , and polythionates are formed from reaction of sulfur with hot aqueous alkali

polythionate

Vulcanization – soft rubber is toughened by cross-linking polyisoprene chains. are dehydrogenated when heated with sulfur and further reaction with occur.

Other reactions of sulfur: - - - 1/8 S 8 + CO O=C=S 1/8 S8 + CN N=C=S ⇌ NΞC-S

Na 2SO 3 + 1/8S 8 –H2O, 373 K Na 2S2O3

S8 + 3AsF 5 – SO 2 [S 8][AsF 6]2 + AsF 3

2+ [S 8] is red and undergoes a change in ring conformation…

2+ [S 8]

7 2+ [S 19 ]

2+ S8

• transannular interactions • Cross ring S-S separations smaller than the sum of van der Waals radii • Two 7-membered, puckered rings • Delocalized bonding connected by a 5- chain • Charge localized on the three- coordinate S

Selenium

4SeCl 2 + 4Ph 3PSe Se 8 + 4Ph 3PCl 2

Inorganic Chemistry By Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman

8 tellurium

4+

2ReCl 4 + 15Te + TeCl 4 –heat in sealed tube → 2[Te 8][ReCl 6]

Production of H 2O2 BaO 2 + H 2SO 4 → BaSO 4 + H2O2

2[NH 4][HSO 4] – electrolytic oxidation, “-H2” [NH 4]2[S 2O8] 2[NH 4][HSO 4] + H 2O2

H2O2 stabilizer

catalytic cycle used in the industrial manufacture of

9 H2O2

H2O2

+ - o H2O2 + 2H + 2e ⇌ 2H 2O E = +1.78 V + - o O2 + 2H + 2e ⇌ H2O2 E = +0.70 V

Cl 2 + H 2O2 → 2HCl + O 2

10 Peroxo complexes

− µ 2− [V(O 2)2(O)(bpy)] [Mo 2(O 2)4(O) 2( -OOH) 2]

11 : H 2SX

n = 2

2H 2S + Sn nCl 2 H2Sn+2 + 2HCl

2- Polysulfides: [S X]

2- [S 6] 2- [Mn(S )(S )] 2- [Zn(S 4)2] 5 6

µ 4- 2- [(S 6)Cu( -S8)-Cu(S 6)] [AuS 9]

12 2- 2- Polyselenides and polytellurides: [Se x] and [Te x]

DMF* 3Se + K 2Se 2 [Se 5] *DMF = =

4Se + K 2Se 2 + 2[Ph 4P]Br [Ph 4P] 2[Se 6] + 2KBr

DMF, 15-crown-5 3 Se + K 2Se 2 [K(15-crown-5)] 2[Se 5] 1,2-diaminoethane, crypt-222 2K + 3 Te [K(crypt-222)] 2[Te 3]

2- 2- [Te 5] [Te 8]

O 141 pm 103° F F

13 Sulfur fluorides and oxofluorides

S2F10

SOF 2

14 Sulfur and oxochlorides

206 pm 1/4S 8(l) + Cl 2(g) - S2Cl 2 193 pm

Reaction Chemistry S 2Cl 2

2SO 2 + S 2Cl 2 + 3Cl 2 4SOCl 2 Cl-S-S 108° SO 3 + SCl 2 SOCl 2 + SO 2 Internal dihedral angle = 84° 2SCl 2  S2Cl 2 + Cl 2

Reaction Chemistry of

SOCl 2

RCO 2H + SOCl 2 RC(O)Cl + SO 2 + HCl

SOCl 2 SO 2Cl 2

15 TeF SeF 4 4 Se 4Cl 16

Tellurium halides

16 2− = MO diagram for octahedral [ECl 6] (E Se or Te)

Oxides of Sulfur

SOCl 2 + Ag 2S -430 K S2O + 2AgCl

HS 7H + SOCl 2 → S8O

S8 ----CF 3C(O)OOH → S8O

17 - [(SO ) N ]- [SO 2N3] 2 3 3

18 form of SO 3 also exists as a trimer of SO 4 units.

Solid state form exists as polymeric chains

Oxides of selenium and tellurium

[Te O F ]3- 3 6 3 SeO 3 tetramer

19 Oxoacids and their salts: S

H2S + HSO 3Cl -low temp- H2S2O3 + HCl

ClSO 3H ClSO 3H H2O2 -HCl H2SO 5 -HCl H2S2O8

20 2− H SO (g) [S 2O6] 2 4

H2SO 4 (l)

Sulfur-Nitrogen Compounds

21 Potential diagrams (values in V) for sulfur, selenium and tellurium at pH = 0.

22