Search results
Results From The WOW.Com Content Network
Oxalate also forms coordination compounds where it is sometimes abbreviated as ox. It is commonly encountered as a bidentate ligand. When the oxalate chelates to a single metal center, it always adopts the planar conformation. As a bidentate ligand, it forms a 5-membered MC 2 O 2 ring. An illustrative complex is potassium ferrioxalate, K 3 [Fe ...
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element.For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory.
Transition metal oxalate complexes are coordination complexes with oxalate (C 2 O 4 2−) ligands. Some are useful commercially, but the topic has attracted regular scholarly scrutiny. Oxalate (C 2 O 4 2-) is a kind of dicarboxylate ligand. [1] As a small, symmetrical dinegative ion, oxalate commonly forms five-membered MO 2 C 2 chelate rings.
In general, 'hard' metal ions prefer weak field ligands, whereas 'soft' metal ions prefer strong field ligands. According to the molecular orbital theory, the HOMO (Highest Occupied Molecular Orbital) of the ligand should have an energy that overlaps with the LUMO (Lowest Unoccupied Molecular Orbital) of the metal preferential.
The greater stabilization that results from metal-to-ligand bonding is caused by the donation of negative charge away from the metal ion, towards the ligands. This allows the metal to accept the σ bonds more easily. The combination of ligand-to-metal σ-bonding and metal-to-ligand π-bonding is a synergic effect, as each enhances the other.
Complexes such as this are called "low spin". For example, NO 2 − is a strong-field ligand and produces a large Δ. The octahedral ion [Fe(NO 2) 6] 3−, which has 5 d-electrons, would have the octahedral splitting diagram shown at right with all five electrons in the t 2g level.
Ligand strength has the following order for these electron donors: weak: iodine < bromine < fluorine < acetate < oxalate < water < pyridine < cyanide:strong. So called "weak field ligands" give rise to small Δ o and absorb light at longer wavelengths.
A transition metal oxo complex is a coordination complex containing an oxo ligand. Formally O 2–, an oxo ligand can be bound to one or more metal centers, i.e. it can exist as a terminal or (most commonly) as bridging ligands. Oxo ligands stabilize high oxidation states of a metal. [1]