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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

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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.

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Production of aluminium in the US between 1960 and 2008.

World production (estimated) and US consumption of gallium between 1980 and 2008

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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.

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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.

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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

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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)

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Adducts of GaH3Adducts of GaH3

Formation of adducts RH2N•GaH3 (R = Me, tBu)

[Al2H6(THF)2] [Al(BH4)3] [Al(BH4)4]−

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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

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[Al7F30]9-[Al7F30]9-

Al2Cl6

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[Al2Cl7]−

Lewis Acid Pigment StabilizationLewis Acid Pigment Stabilization

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Low oxidation state Tl polyatomic ionsLow oxidation state Tl polyatomic ions

[TlCl5]2− [Tl2Cl9]

3−

Al subhalidesAl subhalides

[Al5Br6(THF)6]+ [Al5Br8(THF)4]

−

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metaboric acid, B3O3(OH)3

B2(OH)4

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Borate anionsBorate anions

The structures of selected borate anions

Boron–nitrogen bond distances in selected neutral species

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Boron NitrideBoron Nitride

BorazineBorazine

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B3N3H12

N,N',N''-tBu3-B,B',B''-Ph3B3N3

B(NMe2)3

Aluminum-nitrogen clustersAluminum-nitrogen clusters

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Solid State Metal Boride StructuresSolid State Metal Boride Structures

Solid State Metal Boride Structures, cont.Solid State Metal Boride Structures, cont.

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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

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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

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[B12F12]2-

H2B12(OH)12

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CarbaboranesCarbaboranes