Hexa(tert-butoxy)ditungsten(III)

W₂(O-t-Bu)₆ was first prepared by treating tungsten(III) dialkylamides with tert-butanol.{{Cite journal |last1=Chisholm |first1=M. H. |last2=Extine |first2=M. |date=September 1975 |title=New Metalloorganic Compounds of Tungsten(III) |url=https://pubs.acs.org/doi/abs/10.1021/ja00852a074 |journal=Journal of the American Chemical Society |language=en |volume=97 |issue=19 |pages=5625–5627 |doi=10.1021/ja00852a074 |issn=0002-7863}}

W₂(O-t-Bu)₆ can also be synthesized from NaW₂Cl₇(THF)₅ and NaO-t-Bu.{{Citation |last1=Broderick |first1=Erin M. |title=Dimolybdenum and Ditungsten Hexa(Alkoxides) |date=2014-05-02 |work=Inorganic Syntheses |pages=95–102 |editor-last=Girolami |editor-first=Gregory S. |url=https://onlinelibrary.wiley.com/doi/10.1002/9781118744994.ch18 |access-date=2024-03-08 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9781118744994.ch18 |isbn=978-1-118-74487-1 |last2=Browne |first2=Samuel C. |last3=Johnson |first3=Marc J. A. |last4=Hitt |first4=Tracey A. |last5=Girolami |first5=Gregory S. |editor2-last=Sattelberger |editor2-first=Alfred P.}}

:NaW₂Cl₇(THF)₅ + 6 NaO-t-Bu → W₂(O-t-Bu)₆ + 7 NaCl + 5 THF

As verified by X-ray crystallography, the two tungsten(III) centers are joined by a triple bond. Each W(III) is pseudotetrahedral. The W₂O₆ core adopts a staggered, ethane-like conformation, similar to that for its dimolybdenum analogue. The molecule has inversion symmetry.{{Cite journal |last=Chisholm |first=Malcolm H. |last2=Gallucci |first2=Judith C. |last3=Hollandsworth |first3=Carl B. |date=2006-03-06 |title=Crystal and Molecular Structure of W₂(OBut)₆ and Electronic Structure Calculations on Various Conformers of W₂(OMe)₆ |url=https://www.sciencedirect.com/science/article/pii/S0277538705004870 |journal=Polyhedron |series=Special issue in honour of Michael B. Hursthouse |volume=25 |issue=4 |pages=827–833 |doi=10.1016/j.poly.2005.07.010 |issn=0277-5387}}

This compound hydrolyzes at 200 °C to give WO₂:

:{{chem2|W2(O\st\sBu)6 + 2 H2O -> 2 WO2 + 4 HO\st\sBu + 2 CH2\dC(CH3)2}}

Carbon dioxide reacts reversibly with {{chem2|W2(O\st\sBu)6}} to form green 2:1 adduct featuring two alkyl carbonate ligands.

:{{chem2|W2(O\st\sBu)6 + 2 CO2 <-> W2(O\st\sBu)4(O2CO\st\sBu)2}}

Carbon monoxide react with {{chem2|W2(O\st\sBu)6}} to give {{chem2|W2(O\st\sBu)6CO}}. In this adduct, the carbonyl ligand bridges between two W(III) atoms.. This compound can further react with i-PrOH to generate W₄(μ-CO)₂(O-i-Pr)₁₂. The higher nuclearity of this isopropoxide can be attributed to the smaller size of the isopropoxyl ligands.

{{chem2|W2(O\st\sBu)6}} reacts with alkynes to give RC≡W(O-t-Bu)₃, tetrahedral alkylidyne complexes.{{Cite journal |last=Schrock |first=Richard R. |date=2006-06-02 |title=Multiple Metal–Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture) |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.200600085 |journal=Angewandte Chemie International Edition |language=en |volume=45 |issue=23 |pages=3748–3759 |doi=10.1002/anie.200600085 |pmid=16703641 |issn=1433-7851}} In these complexes, tungsten is electrophilic and the alkylidyne carbon is nucleophilic.{{Cite journal |last1=Listemann |first1=Mark L. |last2=Schrock |first2=Richard R. |date=January 1985 |title=Multiple metal carbon bonds. 35. A General Route to tri-tert-butoxytungsten alkylidyne complexes. Scission of acetylenes by ditungsten hexa-tert-butoxide |url=https://pubs.acs.org/doi/abs/10.1021/om00120a014 |journal=Organometallics |language=en |volume=4 |issue=1 |pages=74–83 |doi=10.1021/om00120a014 |issn=0276-7333}} {{Cite journal |last1=Schrock |first1=Richard R. |last2=Listemann |first2=Mark L. |last3=Sturgeoff |first3=Lynda G. |date=July 1982 |title=Metathesis of Tungsten-Tungsten Triple Bonds with Acetylenes and Nitriles to give alkylidyne and nitrido complexes |url=https://pubs.acs.org/doi/abs/10.1021/ja00379a061 |journal=Journal of the American Chemical Society |language=en |volume=104 |issue=15 |pages=4291–4293 |doi=10.1021/ja00379a061 |issn=0002-7863}}

:{{chem2|W2(O\st\sBu)6 + RC\tCR → 2 RC\tW(O\st\sBu)3}} (R can be Me, Et, Pr)

The reaction proceed in minutes near room temperature. The rate increases in the following order: 4-octyne, 3-hexyne, 2-butyne. The resulting alkylidyne compounds are colorless solids that sublime near room temperature. {{chem2|W2(O\st\sBu)6}} does not react with diphenylacetylene or bis(trimethylsilyl)acetylene. These results are attributed to unfavorable electronic and steric effects, respectively. On the other hand, {{chem2|W2(O\st\sBu)6}} reacts with two equivalents of EtC≡CPh, EtC≡CSiMe₃, and EtC≡C–CH=CH₂ to form corresponding alkylidyne complexes. Thus, {{chem2|W2(O\st\sBu)6}} reacts more easily with asymmetric substitute acetylenes than symmetric ones.

The reactions with alkynes initially afford adducts with a bridging ("μ-perpendicular") alkyne with elongated WW bonds and CC (alkyne) bonds. This intermediate is analogue to other dimetallatetrahedranes. These adducts convert into RC≡W(O-t-Bu)₃. The resulting alkylidyne complexes RC≡W(O-t-Bu)₃ catalyze alkyne metathesis reactions.{{Cite journal |last1=Mortreux |first1=André |last2=Petit |first2=Francis |last3=Petit |first3=Michèle |last4=Szymanska-Buzar |first4=Teresa |date=1995-02-23 |title=Reactions of W(CCMe₃)(OCMe₃)₃ with Terminal Alkynes: Metathesis and Polymerization |url=https://dx.doi.org/10.1016/1381-1169%2894%2900004-2 |journal=Journal of Molecular Catalysis A: Chemical |volume=96 |issue=2 |pages=95–105 |doi=10.1016/1381-1169(94)00004-2 |issn=1381-1169}}

Besides simple metathesis reactions, W₂(O-t-Bu)₆ also reacts with 3-hexyne in a 1:1 molar ratio to form a triangular tritungsten complex compound [W₃(O-t-Bu)₅(μ-O)(μ-CEt)O]₂.{{Cite journal |last1=Cotton |first1=F. Albert |last2=Schwotzer |first2=Willi |last3=Shamshoum |first3=Edwar S. |date=October 1983 |title=A new type of triangular tritungsten cluster compound from reaction of 3-hexyne with hexa-tert-butoxyditungsten |url=https://pubs.acs.org/doi/abs/10.1021/om50004a014 |journal=Organometallics |language=en |volume=2 |issue=10 |pages=1340–1343 |doi=10.1021/om50004a014 |issn=0276-7333}} This reaction has a two steps mechanism; first is the C≡C and W≡W metathesis reaction and follow by formal addition of carbyne (W≡C) to alkoxide (W₂):

W₂(O-t-Bu)₆ + RC≡CR → 2[RC≡W(O-t-Bu)₃]

{{chem2|W2(O\st\sBu)6 + RC\tW(O\st\sBu)3 → W3(O\st\sBu)5(μ\sO)(μ\sCEt)O}}

:{{chem2|W3(O\st\sBu)5(μ\sO)(μ\sCEt)O → [W3(O\st\sBu)5(μ\sO)(μ\sCEt)O]2}}

{{chem2|W2(O\st\sBu)6}} also reacts with EtC≡CC≡CEt to form (t-Bu-O)₃W≡CC≡W(O-t-Bu)₃:

{{chem2|W2(O\st\sBu)6 + EtC\tCC\tCEt → (t\sBu\sO)3W\tCC\tW(O\st\sBu)3 + EtC\tCEt}}

This compound, however, does not act as a metathesis catalyst.

{{chem2|W2(O\st\sBu)6}} also reacts with trans-Pt(C≡CH)₂(PMe₂Ph)₂ to form (t-Bu-O)₃W≡C–C≡W(O-t-Bu)₃ and trans-(PMe₂Ph)₂Pt[C₂W₂(O-t-Bu)₅]₂.{{Cite journal |date=2005 |editor-last=Cotton |editor-first=F. Albert |editor2-last=Murillo |editor2-first=Carlos A. |editor3-last=Walton |editor3-first=Richard A. |title=Multiple Bonds Between Metal Atoms |url=https://link.springer.com/book/10.1007/b136230 |journal=SpringerLink |language=en |doi=10.1007/b136230|isbn=978-0-387-25084-7 }}

With excess amount of nitrile, N≡W(O-t-Bu)₃ is formed along with RC≡CR. The reaction initially gives a 1:1 mixture of the alkylidyne RC≡W(O-t-Bu)₃ and nitride N≡W(O-t-Bu)₃:

:{{chem2|W2(O\st\sBu)6 + RC≡N → RC≡W(O\st\sBu)3 + N≡W(O\st\sBu)3}}

Although W₂(O-t-Bu)₆ reacts with nitriles, it doesn’t react with nitrogen (N≡N).

When C≡C and C≡N bond both exist, W₂(O-t-Bu)₆ reacts more rapidly with C≡N than C≡C bond. Here’s an example of W₂(O-t-Bu)₆ reacting with EtC≡CCN in the presence of quinuclidine:

:{{chem2|W2(O\st\sBu)6 +EtC\tCCN + 12L → EtC\tCC\tW(O\st\sBu)3L + N\tW(O\st\sBu)3}}

On the other hand, the metathesis catalyst MeC≡W(O-t-Bu)₃ reacts more rapidly with C≡C than C≡N bond. Similar reaction with EtC≡CCN and quinuclidine produce different product:

:{{chem2|W2(O\st\sBu)6 + EtC\tCCN + 12 L → NCC≡W(O\st\sBu)3L + EtC≡CMe}}

{{chem2|W2(O\st\sBu)6}} and nitrosobenzene combine to give [W(O-t-Bu)₂(NPh)]₂(μ-O)(μ-O-t-Bu)₂. This reaction undergoes two oxidative additions to form W=N bonds. However, researchers couldn't figure out where the one missing oxygen went. This reaction is the first discovered reaction of a nitroso with metal multiple bonds.{{Cite journal |last1=Cotton |first1=F. Albert |last2=Shamshoum |first2=Edwar S. |date=May 1984 |title=Oxidative addition of nitrosobenzene fragments across the triply bonded ditungsten hexa-tert-butoxide molecule. The preparation and structure of the tungsten-tert-butoxy complex [W(OCMe3)2(NPh)]2(.mu.-O)(.mu.-OCMe3)2 |url=https://pubs.acs.org/doi/abs/10.1021/ja00323a026 |journal=Journal of the American Chemical Society |language=en |volume=106 |issue=11 |pages=3222–3225 |doi=10.1021/ja00323a026 |issn=0002-7863}}

Allenes react with the ditungsten complex forming adducts, e.g.,{{Citation needed|date=February 2025}}

:{{chem2|W2(O\st\sBu)6 + H2C\dC\dCH2 → W2(O\st\sBu)6(HC2\dC\dCH2)}}

Further reaction with carbon monoxide was also demonstrated.

• Hexa(tert-butoxy)dimolybdenum(III)

{{tungsten compounds}}

Category:Alkoxides

Category:Tungsten compounds