Transition metal ether complex


In chemistry, a transition metal ether complex is a coordination complex consisting of a transition metal bonded to one or more ether ligand. The inventory of complexes is extensive. Common ether ligands are diethyl ether and tetrahydrofuran. Common chelating ether ligands include the glymes, dimethoxyethane and diglyme, and the crown ethers. Being lipophilic, metal-ether complexes often exhibit solubility in organic solvents, a property of interest in synthetic chemistry. In contrast, the di-ether 1,4-dioxane is generally a bridging ligand.

Bonding, structure, reactions

Ethers are L-type ligands. They are σ-donors that exert weak field ligands. They resemble water ligands as seen in aquo complexes. They do not, however, readily participate in hydrogen bonding. The ether oxygen is nearly trigonal planar in its complexes.
Being weakly basic, ether ligands tend to be easily displaceable. Otherwise, ether ligands are relatively unreactive. Cyclic ethers such as thf can ring-open or even deoxygenated when bound to highly electrophilic metal halides. Thus treatment of tungsten hexachloride with one equivalent of thf gives 1,4-dichlorobutane:
At higher concentrations of thf, polytetrahydrofuran is produced.

Examples

Homoleptic complexes

Ethers are relatively bulky ligands, thus homoleptic ether complexes are uncommon. Examples often feature weakly coordinating anions such as BArF4− and Al4−.
Metal chloride-tetrahydrofuran complexes are especially studied. These compounds are often reagents because they are soluble in organic solvents as well as being anhydrous.
Formula of
M-Cl-ether complexes		Coordination
sphere		color and comment
ScCl33mer-ScO3Cl3colorless
TiCl42cis-TiO2Cl4yellow
TiCl42cis and trans-TiO2Cl4yellow Both cis and trans isomers have been reported
TiCl33mer-TiO3Cl3blue
2TiO2Cl4green
ZrCl42trans-ZrO2Cl4white
ZrCl42cis-ZrO2Cl4white
HfCl42cis-HfO2Cl4white
VCl33mer-VO3Cl3pink
2trans-VO2Cl4red
NbCl42trans-NbO2Cl4yellow
NbCl42trans-NbO2Cl4yellow
Ta3Cl94TaO2Cl4 and TaOCl5green
CrCl33mer-CrO3Cl3pink
MoCl42trans-MoO2Cl4pink
MoCl42trans-MoO2Cl4beige
MoCl33mer-MoO3Cl3red
WCl33mer-WO3Cl3yellow
WCl42trans-WO2Cl4yellow
MnCl33mer-MnO3Cl3brown-purple
TcCl42cis-TcO2Cl4yellow
ReCl42cis-ReO2Cl4green
Fe4Cl86FeO2Cl3, FeO2Cl4brown
FeCl32FeO2Cl3the related diethyl ether complex is brown
FeCl32FeO2Cl3brown
Co4Cl86CoO2Cl3, CoO2Cl4blue isostructural with Fe analogue
2CoO2Cl3pink
NiCl22cis-NiCl2O4yellow
Copper chloride|nCuO2Cl4, CuOCl4orange
ZnCl22ZnO2Cl2white

Metal carbonyl complexes

  • M5
  • Mo3