Grupo 13 e 14 Organometálicos

Group 13 and 14
• Most dramatic variation in a period from top to bottom (non-metals to metals)
– Oxidation states +3 and +4 – Metals +1,+2

• Light members B,C, Si are important cationicnonmetals • Typically oxophiles and fluorophiles
– borates, silicates, alumina, carbonates

• Readily form alkyl and hydrogen covalent bonds
– boranes, silanes, hydrocarbons

Group 14: Carbon
• Carbonhas vast organic chemistry
– Forms bonds with H and electronegative elements O, S, N, Halogens

• Lack of C-O extended structures • Carbon cluster chemistry
– Fullerenes – Nanotubes

• Carbidechemistry

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C-OH Condensation
• B, Si, Al and many metallic hydroxides condense readily to form extended MO-M polymers and networks
– Siloxanes, alumina, borates

• One explanation:
–Condensation typically requires a coordination+1 intermediate
• protonated or aquated

– i.e. Si(OH)4 forms Si(OH)4(H2O) to form SiO-Si bonds

Carbon Cluster Chemistry
• Relies on C-C covalent bondformation • Simple examples: network structures graphite and diamond • Fullerenes: C2n ranging from n=30-48
– Exciting (overhyped) new allotrope of C – Relatively easily synthesized – C60 I pointgroup
• E, 12 C5, 20 C3, 15 C2

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Reactivity: Halogens
• C60 reacts according to localized double and single bonds, I.e. it isn’t aromatic

Organometallic Fullerenes
• Endohedral Fullerenes
–Caged metal ions Mx@Cn
• Synthesized by laser ablation of C/M surfaces • M includes Sc, Y, La typically in C80, C82, C84

• Fullerene Ligands
– Most transition metals have been bonded tofullerene in varying fashion, – typically as a η2 ligand I.e. similar to double bond not aromatic ring

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Pd(η2 –C60)(PPh3)2

Nanotubes: the Useful Fullerenes
• Discovered shortly after fullerenes •Structuraly can be thought of fullerenes with excess C6 rings stretching out the sphere in one dimension • Very high aspect ratio materials

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Applications
• • • • Nanowires Nanocomposites...