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
1 Borax
Boron 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.
2 Production of aluminium in the US between 1960 and 2008.
World production (estimated) and US consumption of gallium between 1980 and 2008
3 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.
4 Some physical properties of the group 13 elements, M, and their ions. (Continued)
α Part of one layer of the infinite lattice of -rhombohedral boron, showing the B 12 - icosahedral building blocks which are covalently linked to give a rigid, infinite lattice.
5 B 12 B12 +12B
B60
B84 = B 12 B12 B60
β The construction of the B 84 -unit, the main building block of the infinite lattice of - rhombohedral boron. (a) In the centre of the unit is a B 12 -icosahedron, and (b) to each of these 12, another boron atom is covalently bonded. (c) A
B60 -cage is the outer ‘skin’ of the B 84 -unit. (d) The final B 84 -unit can be described in terms of covalently bonded sub-units (B 12 )(B 12 )(B 60 ).
Neutral Group 13 Hydrides
Molecular compounds – BnHm
B2H6 Delocalized 3-center 2-electron B-H-B interactions
6 Selected reactions of B 2H6 and Ga 2H6
GaBH 6
Gas Phase
Solid State
Part of one chain of the polymeric structure of crystalline GaBH 6 (X-ray diffraction at 110 K)
7 Adducts of GaH 3
t Formation of adducts RH 2N•GaH 3 (R = Me, Bu)
− [Al 2H6(THF) 2] [Al(BH 4)3] [Al(BH 4)4]
8 π The formation of partial -bonds in a trigonal planar BX 3 molecule
Reaction of BX 3 with a Lewis base
Boron Halide Clusters
B4Cl 4 B8Cl 8 B9Br 9
The family of BnXn (X = Cl, Br, I) molecules possess cluster structures.
9 9- [Al 7F30 ]
Al 2Cl 6
10 − [Al 2Cl 7]
Lewis Acid Pigment Stabilization
11 Low oxidation state Tl polyatomic ions
2− 3− [TlCl 5] [Tl 2Cl 9]
Al subhalides
+ − [Al 5Br 6(THF) 6] [Al 5Br 8(THF) 4]
12 metaboric acid, B 3O3(OH) 3
B2(OH) 4
13 Borate anions
The structures of selected borate anions
Boron–nitrogen bond distances in selected neutral species
Borazine
15 B3N3H12
t N,N',N''- Bu 3-B,B',B''-Ph 3B3N3
B(NMe 2)3
Aluminum-nitrogen clusters
16 Solid State Metal Boride Structures
Solid State Metal Boride Structures, cont.
17 Electron-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 2- 2- general formula [BnHn] (e.g. [B 6H6] ). Nido-cluster – atoms form an open cage, derived from closed cage by - removing one vertex, and have the general formula B nHn+4 , [B nHn+3 ] (e.g. - B5H9, [B 5H8] ). Arachno-cluster – atoms form an open cage, derived from closed cage - with two vertices unoccupied, and have the general formula BnHn+8 , [B nHn+5 ] - (e.g. B 4H10 , [B 4H9] ). Hypho-cluster – atoms form an open cage, derived from closed cage with - three vertices unoccupied, and have the general formula BnHn+8 , [B nHn+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. {B 5H8}2) *Deltahedron is a polyhedron that possesses only triangular faces (e.g. octahedron)
Electron-deficient clusters
closo nido arachno
18 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
19 20 2- [B 12 F12 ]
H2B12 (OH) 12
21 22 Carbaboranes
23