Halide and Oxide Structures

A majority of halides and oxides comprise the structures supposed for largely ionic compounds, along with the metal in octahedral coordination. General oxide structures are rocksalt (example MnO, NiO), corundum and rutile (example TiO₂, CrO₂). Several MF₂ compounds contain the rutile structure, another dihalides forming layer (CdCl₂ and CdI₂) types. Several ternary oxides and halides also follow this pattern; for instance, the LaMO₃ compounds formed through all elements of the series (M=Sc-Cu) comprise the perovskite structure.

The 3d⁴ ions Cr²⁺ and Mn³⁺ and the 3d⁹ ion Cu²⁺ are matter to Jahn-Teller distortions. For instance, CuO does not comprise the rocksalt structure, but one with 4 close Cu-O neighbors and two at longer distance; identical tetragonally distorted coordination is arrive in several other simple compounds of Cr²⁺ and Cu²⁺. (Note that CrO is not known.)

Tetrahedral coordination is also occasionally found. In high oxidation states (example molecular TiCl₄, polymeric CrO₃ and in complex ions like VO^3-_4, CrO^2-₄and MnO₄^-) this can be understood in terms of the small size of the transition metal ion. Though, tetrahedral (zinc blende) structures are also found in Cu^I halides like CuCl. As Cu⁺ has the 3d¹⁰ configuration this come onto existence to be typical post-transition metal behavior as seen, for instance, with Zn²⁺, and must include some degree of covalent bonding.

A few ternary and mixed-valency oxides comprise the spinel structure in which metal ions take place a proportion of tetrahedral and octahedral holes with in a cubic close-packed lattice. Instances include M₃O₄ with M=Mn, Fe, Co. The distribution of M³⁺ and M²⁺ ions among the tetrahedral and octahedral sites depicts the affect of ligand field stabilization energies. In Fe₃O₄, Fe²⁺ (3d⁶) have an octahedral preference where Fe³⁺ (3d⁵) has none, and this compound have the opposite spinel structure where Fe²⁺ is octahedral and Fe³⁺ is exist in both octahedral and tetrahedral sites. In Co₃O₄ the low-spin 3d⁶ ion Co³⁺ comprise a very strong octahedral preference and the general spinel structure is found with all Co³⁺ in octahedral sites and Co²⁺ tetrahedral. Mn₃O₄ is as well based on the normal spinel structure, but with a tetragonal distortion as supposed for the sites occupied through Mn³⁺ (3d⁴).