Coordination number 3

   3-Coordinate complexes are not common. Usually, trigonal planar structures are observed, and examples involving d10 metal centres include:

• Cu(I) in [Cu(CN)₃]^2-  (19.2), [CuCN)₂]^- (see above), [CuSPMe₃)₃]⁺ ;
• Ag(I) in [AgTe₇]^3- (Figure 19.4b),[AgPPh₃)₃]⁺;
• Au(I) in [Au{PPh(C₆H₁₁)₂}₃] ⁺;
• Hg(II) in [HgI₃]^-, [HgSPh₃)₃]^- ;
• Pt(0) in [PtPPh₃)₃], [PtP ^tBu₂H)₃].

   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.

مواضيع ذات صلة

ايجاد الصيغة التركيبية للمعقدات

معقدات الخارصين

معقدات النحاس

كيمياء ومعقدات بعض عناصر السلسلة الانتقالية الاولى

تعريف المركبات المعقدة

Crystal Field Stabilization Energies

Colors of Transition-Metal Complexes

The Nature of the Ligands

Principal Quantum Number of the Metal

Charge on the Metal Ion

Factors That Affect the Magnitude of Δo

Electronic Structures of Metal Complexes