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Date: 28-2-2017
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Date: 28-11-2016
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Date: 17-8-2016
550
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Coordination number 3
3-Coordinate complexes are not common. Usually, trigonal planar structures are observed, and examples involving d10 metal centres include:
Sterically demanding amido ligands have been used to stabilize complexes containing 3-coordinate metal ions, e.g. [Fe{N(SiMe3)2}3] (Figure 19.4c). In the solid state, [Y{N(SiMe3)2}3] and [Sc{N(SiMe3)2}3] possess trigonal pyramidal metal centres (∠N–Y–N = 1150 and N–Sc–N = 115.50), but it is likely that crystal packing effects cause the deviation from planarity. The fact that in the gas phase [Sc{N(SiMe3)2}3] contains a trigonal planar Sc(III) centre tends to support this proposal. p-Block chemistry has a number of examples of T-shaped molecules (e.g. ClF3) in which stereochemically active lone pairs play a crucial role. d-Block metal complexes do not mimic this behaviour, although ligand constraints (e.g. the bite angle of a chelate) may distort a 3-coordinate structure away from the expected trigonal planar structure.
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