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 14 Boron Nitride 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.