View
227
Download
8
Category
Preview:
Citation preview
1
Chapter 13
Group 13 Elements
Physical Properties
Metals
Halides, oxides, hydroxides, salts of oxoacids
Compounds containing nitrogen
Metal boride
Electron deficient borane and carborane clusters: an introduction
2
Boron
Borax
Relative abundances of the group 13 elements in the Earth’s crust.
http://www.astro.virginia.edu/class/oconnell/LBT/
Abundances of elements in the Earth’s crusts.
3
Production of aluminium in the US between 1960 and 2008.
World production (estimated) and US consumption of gallium between 1980 and 2008
4
Uses of aluminium in the US in 2008
Uses of boron in the US in 2008
Some physical properties of the group 13 elements, M, and their ions.
5
Some physical properties of the group 13 elements, M, and their ions. (Continued)
Part of one layer of the infinite lattice of α-rhombohedral boron, showing the B12-icosahedral building blocks which are covalently linked to give a rigid, infinite lattice.
6
B12 B12+12B
B60
B84 = B12B12B60
The construction of the B84-unit, the main building block of the infinite lattice of β-rhombohedral boron. (a) In the centre of the unit is a B12-icosahedron, and (b) to each of these 12, another boron atom is covalently bonded. (c) A B60-cage is the outer ‘skin’ of the B84-unit. (d) The final B84-unit can be described in terms of covalently bonded sub-units (B12)(B12)(B60).
Neutral Group 13 HydridesNeutral Group 13 Hydrides
B2H6
Delocalized 3-center 2-electron B-H-B interactions
Molecular compounds – BnHm
7
Selected reactions of B2H6 and Ga2H6
GaBH6GaBH6
Gas Phase
Solid State
Part of one chain of the polymeric structure of crystalline GaBH6 (X-ray diffraction at 110 K)
8
Adducts of GaH3Adducts of GaH3
Formation of adducts RH2N•GaH3 (R = Me, tBu)
[Al2H6(THF)2] [Al(BH4)3] [Al(BH4)4]−
9
The formation of partial π-bonds in a trigonal planar BX3 molecule
Reaction of BX3 with a Lewis base
Boron Halide ClustersBoron Halide Clusters
The family of BnXn (X = Cl, Br, I) molecules possess cluster structures.
B4Cl4 B8Cl8 B9Br9
12
Low oxidation state Tl polyatomic ionsLow oxidation state Tl polyatomic ions
[TlCl5]2− [Tl2Cl9]
3−
Al subhalidesAl subhalides
[Al5Br6(THF)6]+ [Al5Br8(THF)4]
−
14
Borate anionsBorate anions
The structures of selected borate anions
Boron–nitrogen bond distances in selected neutral species
16
B3N3H12
N,N',N''-tBu3-B,B',B''-Ph3B3N3
B(NMe2)3
Aluminum-nitrogen clustersAluminum-nitrogen clusters
17
Solid State Metal Boride StructuresSolid State Metal Boride Structures
Solid State Metal Boride Structures, cont.Solid State Metal Boride Structures, cont.
18
Electron-deficient clustersElectron-deficient clusters
Electron deficient clusters possess fewer valence electrons than are required for a localized bonding scheme. In a cluster, the atoms form a cage-like structure.
Closo-cluster – atoms form a closed, deltahedral* cage and have the general formula [BnHn]2- (e.g. [B6H6]2-).
Nido-cluster – atoms form an open cage, derived from closed cage by removing one vertex, and have the general formula BnHn+4, [BnHn+3]- (e.g. B5H9, [B5H8]-).
Arachno-cluster – atoms form an open cage, derived from closed cage with two vertices unoccupied, and have the general formula BnHn+8, [BnHn+5]-
(e.g. B4H10, [B4H9]-).
Hypho-cluster – atoms form an open cage, derived from closed cage with three vertices unoccupied, and have the general formula BnHn+8, [BnHn+7]-.
Conjuncto-cluster – consists of two or more open cages connected together through a shared atom, an external bond, a shared edge or a shared face (e.g. {B5H8}2)
*Deltahedron is a polyhedron that possesses only triangular faces (e.g. octahedron)
Electron-deficient clustersElectron-deficient clusters
closo nido arachno
19
Wade’s rules
•A closo-deltahedral cluster cage with n vertices requires (n+1) pairs of electrons, which occupy (n+1) cluster bonding MOs.
•From a parent closo cage with n vertices, a set of more open cages (nido, arachno, and hypho) can be derived, each of which possessed (n+1) pairs of electrons occupying (n+1) cluster bonding MOs
•For a parent closo-deltahedron with n vertices, the related nido-cluster has (n-1) vertices and (n+1) pairs of electrons
•For a parent closo-deltahedron with n vertices, the related arachno-cluster has (n-2) vertices and (n+1) pairs of electrons
•For a parent closo-deltahedron with n vertices, the related hypho-cluster has (n-3) vertices and (n+1) pairs of electrons
deltahedral cages
Recommended