transition metal ether complex
File:VEHZAJ.svg | year = 1990 | volume = C46 | pages = 890–2 | doi = 10.1107/S010827018901382X | last1 = Duraj | first1 = S. A. | last2 = Towns | last3 = Baker | last4 = Schupp | first4 = J. | issue = 5| doi-access = }}]]
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.{{Greenwood&Earnshaw2nd}} Common ether ligands are diethyl ether and tetrahydrofuran. Common chelating ether ligands include the glymes, dimethoxyethane (dme) 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
File:CoCl2(dioxane)XUBHEI).jpg of cobalt(II) chloride and 1,4-dioxane.{{cite journal |doi=10.1021/ja902101x|title=Crystal-to-Crystal Transformation from Antiferromagnetic Chains into a Ferromagnetic Diamondoid Framework |year=2009 |last1=Duan |first1=Zhiming |last2=Zhang |first2=Yan |last3=Zhang |first3=Bin |last4=Zhu |first4=Daoben |journal=Journal of the American Chemical Society |volume=131 |issue=20 |pages=6934–6935 |pmid=19402661 }}]]
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:{{cite journal |doi=10.1016/j.poly.2016.07.024|year=2016 |volume=117 |last1=Bianchi |first1=Sabrina |last2=Bortoluzzi |first2=Marco |last3=Castelvetro |first3=Valter |last4=Marchetti |first4=Fabio |last5=Pampaloni |first5=Guido |last6=Pinzino |first6=Calogero |last7=Zacchini |first7=Stefano |title=The reactivity of tungsten hexachloride with tetrahydrofuran and 2-methoxyethanol |journal=Polyhedron |pages=769–776 |hdl=11568/803763 |hdl-access=free }}
:{{chem2|WCl6 + OC4H8 -> WOCl4 + ClCH2CH2CH2CH2Cl}}
At higher concentrations of thf, polytetrahydrofuran is produced.
Examples
=Homoleptic complexes=
Ethers are relatively bulky ligands, thus homoleptic (i.e., all ligands being the same) ether complexes are uncommon. Examples often feature weakly coordinating anions such as BArF4− and Al(ORF)4−.
- [V(thf)6](BArF4)2{{cite journal |doi=10.1002/(SICI)1521-3773(19981204)37:22<3169::AID-ANIE3169>3.0.CO;2-0|title=Cationic Homoleptic Vanadium(II), (IV), and (V) Complexes Arising from Protonolysis of [V(NEt2)4] |year=1998 |last1=Choukroun |first1=Robert |last2=Moumboko |first2=Pierre |last3=Chevalier |first3=Sandrine |last4=Etienne |first4=Michel |last5=Donnadieu |first5=Bruno |journal=Angewandte Chemie International Edition |volume=37 |issue=22 |pages=3169–3172 |pmid=29711321 }}
- [Mn(thf)6](Mn(CO)5]2{{cite journal |doi=10.1021/ja00117a019|title=An Unusual Transition Metal Cluster Containing a Seven Metal Atom Plane. Syntheses and Crystal Structures of [Mn][Mn7(THF)6(CO)12]2, Mn3(THF)2(CO)10, and [Mn(THF)6][Mn(CO)5]2 |year=1995 |last1=Kong |first1=Gapgoung |last2=Harakas |first2=George N. |last3=Whittlesey |first3=Bruce R. |journal=Journal of the American Chemical Society |volume=117 |issue=12 |pages=3502–3509 }}
- Fe(thf)6[BArF24]2{{cite journal |doi=10.1021/acs.organomet.5b00395|title=Mono- and Dinuclear Neutral and Cationic Iron(II) Compounds Supported by an Amidinato-diolefin Ligand: Characterization and Catalytic Application |year=2015 |last1=Lichtenberg |first1=Crispin |last2=Adelhardt |first2=Mario |last3=Wörle |first3=Michael |last4=Büttner |first4=Torsten |last5=Meyer |first5=Karsten |last6=Grützmacher |first6=Hansjörg |journal=Organometallics |volume=34 |issue=12 |pages=3079–3089 }}
- [Ni(thf)6][Al(ORF)4 ]2{{cite journal |doi=10.1002/zaac.201700367|title=Reactivity of [Ni(cod)2][Al(ORF)4] towards Small Molecules and Elements |year=2018 |last1=Schwab |first1=Miriam M. |last2=Himmel |first2=Daniel |last3=Kacprzak |first3=Sylwia |last4=Radtke |first4=Valentin |last5=Kratzert |first5=Daniel |last6=Yassine |first6=Zeinab |last7=Weis |first7=Philippe |last8=Weber |first8=Stefan |last9=Krossing |first9=Ingo |journal=Zeitschrift für Anorganische und Allgemeine Chemie |volume=644 |pages=50–57 }}
=Metal halide complexes=
File:NiI2(dme)2.png. The sum of the angles at O is 352°, indicating a nearly planar ether oxygen. Color code: O = red, I = purple, Ni = blue, C = black.{{cite journal |doi=10.1002/zaac.201000022|title=Polyether Adducts of d-Block Metal Compounds as Starting Materials for New Cluster Compounds |year=2010 |last1=Crochet |first1=Aurélien |last2=Fromm |first2=Katharina M. |journal=Zeitschrift für anorganische und allgemeine Chemie |volume=636 |issue=8 |pages=1484–1496 |url=http://doc.rero.ch/record/20544/files/fro_pad.pdf }}]]
Metal chloride-tetrahydrofuran complexes are especially studied.{{cite book |doi=10.1002/9780470132524.ch31|title=Tetrahydrofuran Complexes of Selected Early Transition Metals|series=Inorganic Syntheses|year=1982|last1=Manzer|first1=L. E.|pages=135–140|volume=21}} These compounds are often reagents because they are soluble in organic solvents as well as being anhydrous.
=Metal carbonyl complexes=
- M(CO)5(thf) (M = Cr, Mo, W){{cite journal |doi=10.1016/S0022-328X(00)84160-1|title=Kristall- und molekülstruktur von pentacarbonyltetrahydrofuran-chrom(0) |year=1978 |last1=Schubert |first1=U. |last2=Friedrich |first2=P. |last3=Orama |first3=O. |journal=Journal of Organometallic Chemistry |volume=144 |issue=2 |pages=175–179 }}
- Mo(CO)3(diglyme)