Grupo 13 e 14 Organometálicos
• 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
1
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
2
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
3
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
4
Applications
• • • • Nanowires Nanocomposites...
Regístrate para leer el documento completo.