Transition metal oxo complex

One of the earliest synthetic compounds to incorporate an oxo ligand is potassium ferrate (K2FeO4), which was likely prepared by Georg E. Stahl in 1702.

[2] A common reaction exhibited by metal-oxo compounds is olation, the condensation process that converts low molecular weight oxides to polymers with M-O-M linkages.

[4] Some of the longest known and most widely used oxo compounds are oxidizing agents such as potassium permanganate (KMnO4) and osmium tetroxide (OsO4).

[5] Compounds such as these are widely used for converting alkenes to vicinal diols and alcohols to ketones or carboxylic acids.

Although there is some variation among these enzymes, members from all three families involve oxygen atom transfer between the Mo/W center and the substrate.

[16] The active site for the oxygen-evolving complex (OEC) of photosystem II (PSII) is a Mn4O5Ca centre with several bridging oxo ligands that participate in the oxidation of water to molecular oxygen.

[17] The OEC is proposed to utilize a terminal oxo intermediate as a part of the water oxidation reaction.

[18] Terminal oxo ligands are also rather rare for the titanium triad, especially zirconium and hafnium and are unknown for group 3 metals (scandium, yttrium, and lanthanum).

a) Doubly bridging and b) terminal oxo ligands
Sodium decavanadate , one of many polyoxometallate salts. The structure illustrates terminal oxo, doubly-bridging oxo, triply bridging oxo, and six-fold bridging oxo ligands.
Selection of molecular metal oxides. From left, vanadyl chloride (d 0 ), a tungsten oxo carbonyl (d 2 ), permanganate (d 0 ), [ReO 2 (pyridine) 4 ] + (d 2 ), simplified view of compound I (a state of cytochrome P450 , d 4 ), and Ir(O)(mesityl) 3 (d 4 ). [ 7 ]
Oxygen rebound mechanism used by cytochrome P450 enzymes for oxidation of aliphatic groups to alcohols by the action of Compound I (adapted from [ 8 ]
Three structural families of molybdenum cofactors: a) xanthine oxidase, b) sulfite oxidase, and c) (DMSO) reductase . The DMSO reductase features two molybdopterin ligands attached to molybdenum. They are omitted from the figure for simplicity. The rest of the heterocycle is similar to what is shown for the other two cofactors.
X-ray Crystal structure of the Mn 4 O 5 Ca core of the oxygen evolving complex of Photosystem II at a resolution of 1.9 Å. [ 17 ]
Qualitative molecular orbital diagram of a d 0 metal-oxo fragment (empty metal d orbitals in an octahedral field on left, full oxygen p orbitals on right). Here it can be seen that d 1-2 electrons fill a nonbonding orbital and electrons d 3-6 fill anti-bonding orbitals, which destabilize the complex. [ 18 ]