transition metal carbyne complex

Transition metal carbyne complexes are most common for the early transition metals, especially niobium, tantalum, molybdenum, tungsten, and rhenium. They can also have low-valence metals as well as high-valence metals.

File:VinylideneToCarbyne.png

The first Fischer carbyne complex was reported in 1973.{{cite journal|first1=E. O. |last1=Fischer |first2=G. |last2=Kreis |first3=C. G. |last3=Kreiter |first4=J. |last4=Muller |first5=G. |last5=Huttner |first6=H. |last6=Lorenz|journal= Angew. Chem. |date=1973 |volume=85|issue=14 |pages=618–620|title=trans-Halogeno-alkyl(aryl)carbin-tetracarbonyl-Komplexe von Chrom, Molybdän und Wolfram–Ein neuer Verbindungstyp mit Übergangsmetall-Kohlenstoff-Dreifachbindung|trans-title=trans-Halogenoalkyl(aryl)carbynetetracarbonyl complexes of chromium, molybdenum and tungsten–A new type of compound with a transition metal–carbon triple bond|doi=10.1002/ange.19730851407|bibcode=1973AngCh..85..618F }} Two years later in 1975, the first "Schrock carbyne" was reported.{{cite journal|first1=L. J. |last1=Guggenberger |first2=R. R. |last2=Schrock |journal=J. Am. Chem. Soc. |date=1975 |volume=97 |issue=10 |pages=2935|title=Tantalum carbyne complex |doi=10.1021/ja00843a072}}

Many high-valent carbyne complexes have since been prepared, often by dehydrohalogenation of carbene complexes. Alternatively, amino-substituted carbyne ligands sometimes form upon protonation of electron-rich isonitrile complexes. Similarly, O-protonation of μ₃-CO ligands in clusters gives hydroxycarbyne complexes. Vinyl ligands have been shown to rearrange into carbyne ligands. Addition of electrophiles to vinylidene ligands also affords carbyne complexes.

File:HCCo3(CO)9.png (formula: HCCo₃(CO)₉) is a metal cluster that contains the methylidyne ligand.]]

Some metal carbynes dimerize to give dimetallacyclobutadienes. In these complexes, the carbyne ligand serves as a bridging ligand.

Several cluster-bound carbyne complexes are known, typically with CO ligands. These compounds do not feature MC triple bonds; instead the carbyne carbon is tetrahedral. Tricobalt derivatives are prepared by treating cobalt carbonyl with haloforms:{{cite book |first1=Dietmar |last1=Seyferth |first2=Mara O. |last2=Nestle |first3=John S. |last3=Hallgren |title=Inorganic Syntheses |chapter=μ₃ -Alkylidyne-Tris(Trigarbonylcobalt) Compounds: Organocobalt Cluster Complexes |journal=Inorg. Synth. |date=2007 |volume=20 |pages=224 224–226] |doi=10.1002/9780470132517.ch52|isbn=9780470132517 }}

:2 HCBr₃ + {{frac|9|2}} Co₂(CO)₈ → 2 HCCo₃(CO)₉ + 18 CO + 3 CoBr₂

File:COXVOA10.png

Monomeric metal carbyne complexes exhibit fairly linear M–C–R linkages according to X-ray crystallography. The M–C distances are typically shorter than the M–C bonds found in metal carbenes. The bond angle is generally between 170° and 180°.{{cite book|title=Organometallic Chemistry |edition=2nd |last1=Spessard |first1=Gary O. |last2=Miessler |first2=Gary L. |pages=439–449 |isbn=9780199342679|year=2015 |publisher=Oxford University Press }} Analogous to Fischer and Schrock carbenes; Fischer and Schrock carbynes are also known. Fischer carbynes usually have lower oxidation state metals and the ligands are π-accepting/electron-withdrawing ligands. Schrock carbynes on the other hand typically have higher oxidation state metals and electron-donating/anionic ligands. In a Fischer carbyne the C-carbyne exhibits electrophilic behavior while Schrock carbynes display nucleophilic reactivity on the carbyne carbon.{{cite book|first1=R. H. |last1=Crabtree |title=The Organometallic Chemistry of the Transition Metals |edition=6th |pages=290–315 |publisher=Wiley |location=New York, NY |date=2014 |isbn=9781118138076}} In 2025, radical reactivity at the carbyne carbon was also reported.{{Citation |last=Deng |first=Zhihong |title=Radical Additions of Carbyne to Achieve Metalla-aromatic Radicals |date=2025-04-21 |url=https://chemrxiv.org/engage/chemrxiv/article-details/67ff9e16927d1c2e6639c262 |access-date=2025-05-14 |publisher=ChemRxiv |language=en |doi=10.26434/chemrxiv-2025-gw265 |last2=Ye |first2=Shengfa |last3=Jiang |first3=Xuelian |last4=Zhang |first4=Xinchao |last5=Chen |first5=Dafa |last6=Huang |first6=Zhe |last7=Tao |first7=Lizhi |last8=Liu |first8=Jiaojiao |last9=Ni |first9=Yong|url-access=subscription |doi-access=free }} Carbyne complexes have also been characterized by many methods including infrared Spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction.{{cite book|title=Transition Metal Carbyne Complexes |last=Kreißl |first=F. R. |date=5 December 2012 |publisher=Springer |isbn=9789401047289}} Bond lengths, bond angles and structures can be inferred from these and other analytical techniques.

Metal carbyne complexes also exhibit a large trans effect, where the ligand opposite the carbyne is typically labile.

Hexa(tert-butoxy)ditungsten(III) is a catalyst for alkyne metathesis.{{Cite journal |last=Fürstner |first=Alois |date=2021-09-29 |title=The Ascent of Alkyne Metathesis to Strategy-Level Status |journal=Journal of the American Chemical Society |language=en |volume=143 |issue=38 |pages=15538–15555 |doi=10.1021/jacs.1c08040 |issn=0002-7863 |pmc=8485352 |pmid=34519486}} The catalytic cycle involves an carbyne intermediate.{{cite journal |doi=10.1021/om00120a014|title=Multiple metal carbon Bonds. 35. A General Route to tri-tert-Butoxytungsten Alkylidyne complexes. Scission of Acetylenes by Ditungsten Hexa-tert-butoxide|year=1985|last1=Listemann|first1=Mark L.|last2=Schrock|first2=Richard R.|journal=Organometallics|volume=4|pages=74–83}}

Some carbyne complexes react with electrophiles at C-carbyne followed by association of the anion. The net reaction gives a transition metal carbene complex:

:L_nM≡CR + HX → L_n(X)M=CHR

These complexes can also undergo photochemical reactions.

In some carbyne complexes, coupling of the carbyne ligand to a carbonyl is observed. Protonation of the carbyne carbon and conversion of the carbyne ligand into a π-allyl.{{cite journal|first1=K. B. |last1=Kingsbury |first2=J. D. |last2=Carter |first3=L. |last3=McElwee-White |journal=J. Chem. Soc., Chem. Commun. |date=1990|volume=1990 |issue=8 |pages=624–625|title=Formation of cyclopentenone upon photo-oxidation of the cyclopropyl (c-C₃H₅) carbyne complex [(η⁵-C₅H₅){P(OMe)₃}(CO)W≡C(c-C₃H₅)]|doi=10.1039/C39900000624 }}

A sulfur-based main group analog of a carbyne complex has been prepared by Seppalt and coworkers.{{Cite journal|last1=Poetter|first1=Brigitte|last2=Seppelt|first2=Konrad|last3=Simon|first3=Arndt|last4=Peters|first4=Eva Maria|last5=Hettich|first5=Bernhard|date=February 1985|title=Trifluoroethylidynesulfur trifluoride, CF3C.tplbond.SF3, and its dimer|journal=Journal of the American Chemical Society|language=en|volume=107|issue=4|pages=980–985|doi=10.1021/ja00290a038|issn=0002-7863}} The compound, trifluoro(2,2,2-trifluoroethylidyne)-λ⁶-sulfurane, F₃C–C≡SF₃, prepared by dehydrofluorination of F₃C–CH=SF₄ or F₃C–CH₂–SF₅, is an unstable gas that readily undergoes dimerization to form trans-(CF₃)(SF₃)C=C(CF₃)(SF₃) at above –50 °C.

• {{cite book|first1=A. |last1=Mayr |first2=C. M. |last2=Bastos |journal=Prog. Inorg. Chem. |volume=40|pages=1–98 |date=1992|title=Coupling Reactions of Terminal Two-Faced π Ligands and Related Cleavage Reactions|doi=10.1002/9780470166413.ch1|series=Progress in Inorganic Chemistry |isbn=9780470166413 }}

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Category:Organometallic chemistry

Category:Coordination chemistry

Category:Transition metals