CH 411/511 Intro 1

Ch 14. Group 14

Elemental forms

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CH 411/511 Intro 2

Diamond structured metals

Eg /eV R/ cmg

C 5.5 insulator 1015

Si 1.1 semicon 50

Ge 0.6 semicon 30

Sn small metallic 10−5

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Discovery of fullerenes

+

fullerenes

4From “Designing the Molecular World” by Phillip Ball, Princeton, 1994

www.chemistry.oregonstate.edu/courses/ch412/gobeavs/bucky.ppt

CH 411/511 Intro 3

Icosahedral symmetry

C60 indicating reactive p-

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reactive porbitals

Fullerenes

C60 soln C70 soln

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FCC solid structure

CH 411/511 Intro 4

C60 reduction

C li

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Cyclicvoltammetry

Fullerene derivatives

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(2C70fullerene)carbonylchlorobis(triphenylphosphine)iridium

Balch, Catalano, Lee, Olmstead, Parkin, JACS 113, 8953,1991.

[Pt(PPh3)2(C60)]

CH 411/511 Intro 5

Carbon Nanotubes

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Multi-walled nanotube (MWNT)End-closed Sm2O3 in nanotube

Bond enthalpies

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CH 411/511 Intro 6

Heavier congeners

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Halides

CF4 not a LA

SiFSiF4

GeF4

SnF4

PbF4

ex SiF4 + 2HF H2SiF6

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Note: PbF4 is a strong oxidant due to inert pair effect

All readily hydrolyze in air - except CF4

CH 411/511 Intro 7

PbF4 and PbO

PbO

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PbO

Carbides

CaCCaC2

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CH 411/511 Intro 8

Polyanion clusters

Zintl ions

Pb52

using Wades’ rules for e counting

# e pairs = ½ (5 (2) + 2) = 6 which is (n+1) or closo

Sn94

# e pairs = ½ (9 (2) + 4) = 11 which is (n+2) nido

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# e pairs = ½ (9 (2) + 4) = 11 which is (n+2) nido

These are strong reducing agents, prepared in NH3

(anhyd, liq) or H2NCH2CH2NH2 (anhyd, liq)

Graphite structure

• C C in plane = 1 42 Å• C-C in-plane = 1.42 Å• Usually (AB)n hexgonal

stacking• Interlayer distance

= 3.354 Å

Graphite is a

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Source: http://www.ccs.uky.edu/~ernst/

A

B

A

Graphite is a semi-metal, chemically stable, light, strong

CH 411/511 Intro 9

Graphite Intercalation

Cx → Cx+ + e− E ~ −1.3 V

(so no Cx+An− compounds in aqu solution)

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Cx + BF3 + ½ F2 CxBF4

Cx + AlCl3 + 1/2Cl2 CxAlCl4Domain structure

Some acceptor-type GIC’s

Blue: obsPink: calc

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CxB(O2C2(CF3)4)2

Pink: calc

CxSO3C8F17

CH 411/511 Intro 10

Graphite Lithiation

Graphite lithiation: approx 0.2-0.3 V vs Li+/Li

Expands about10% along z

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Theoretical capacity:Li metal > 1000 mAh/gC6Li 370

Actual C6Li formation: 320 – 340 mAh/g reversible;20 – 40 irreversible

Lithium ion batteries

C th dCathode LiCoO2 Li1-xCoO2 + xLi+ + xe-

Anode6C + Li+ + e- C6Li

ElectrolyteOrganic solvent with LiPF6

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g 6

CH 411/511 Intro 11

Orthosilicates

Basic unit is SiO4 (Td) Si4+, O2−

MgxMnyFe2-x-ySiO4 (peridot)

green color from Fe(II)

Ortho = isolated SiO44− ions

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hcp O array, Si in 1/8 Td sites and Mg,Fe,Mn in 1/2 Oh sites

Single chain metasilicates

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NaAl(SiO3)2

Jadeite

(SiO32−)n

shared O has no chargeapical O has 1− charge

CH 411/511 Intro 12

Double chain metasilicates

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Beryl structure

Si6O1812− = (SiO3

2−)6 ring

Be3Al2Si6O18 is beryl

Be3Al2−xCrxSi6O18 is emerald

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CH 411/511 Intro 13

Sheet silicates

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mica 2:1 clay minerals

Clays

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CH 411/511 Intro 14

Clay minerals

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3D frameworks

-quartz varieties include amethyst, agate.

Also tridymite, cristobalite

SiO2

y ,

All corner sharing Td

MP ~1700 C

Due to slow rearrangement to crystallize, these readily form amorphous glass (vitreous silica)

Borosilicates – add Na2O B2O3 as network

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Borosilicates add Na2O, B2O3 as network modifiers (Pyrex)

CH 411/511 Intro 15

3D frameworks - aluminosilicates

Zeolite A

corner sharing Td with Al substitution for Si, which

Sodalite cages = (Al3Si)24O48

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gives negative charge on framework

Nax[(AlO2)x(SiO2)] · δ H2O x < 1 (no Al-O-Al links)

Zeolite frameworks

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Na2SiO3 (hyd) + NaAlO2 (hyd) → NaAlSiO4(hyd)

N(OEt)3

CH 411/511 Intro 16

Siloxanes

Si + 2CH Cl (CH ) SiClSi + 2CH3Cl (CH3)2SiCl2

Controlled hydrolysis to [(CH3)SiO]n + 2 HCl

Si3O3(CH3)6 [(CH3)2SiO]n polydimethylsiloxane (silicone)

Some additives (CH3)3SiCl chain termination

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Some additives (CH3)3SiCl chain termination

CH3SiCl3 crosslinker

(CH3)(C6H5)SiCl2 phenyl groups increasecrystallinity and modulus

Siloxanes

8 CH3SiCl3 + 12 H2O → cyclo-(CH3)8Si8O12 + 24 HCl

Cubic arrangement

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