Transition metal alkenyl complex

Last updated

A transition metal alkenyl complex is an organometallic compound containing a metal bound to a alkenyl group (i.e., the motif M-CR=CRR'). The simplest alkenyl ligand is vinyl. [1]

Contents

Ligand properties

Examples of common bonding modes for alkenyl ligands (Me = methyl). TwoM-vinyls.svg
Examples of common bonding modes for alkenyl ligands (Me = methyl).

According to the covalent bond classification method, a terminal alkenyl is an anionic X-type ligand. [2]

Some alkenyl ligands are bridging ligands, in which case they provide 3 electrons to the pair of metals. [3] A third class of alkenyl ligands bind in an η2- mode. They are also 3-electron ligands. [4]

Two resonance structures for an e -vinyl molybdenum trimethylphosphite complex (Ph = phenyl). Eta-2 vinylMo.svg
Two resonance structures for an η -vinyl molybdenum trimethylphosphite complex (Ph = phenyl).

Synthesis and occurrence

In the laboratory preparations, alkenyl complexes are often prepared by salt metathesis using vinyl lithium or vinyl Grignard reagents. They also arise by protonation of alkyne complexes. Oxidative addition of vinyl halides gives alkenyl complexes: [5]

CH2=CHBr + Pd(PPh3)4 → PdBr(CH=CH2)(PPh3)2 + 2 PPh3 (Ph = phenyl)

Homoleptic vinyl complexes are unknown, but a trivinyl complex has been characterized. [6]

Metal alkenyl complexes are intermediates in the semihydrogenation of alkynes to alkenes [7]

References

  1. ↑ Hartwig, John F. (2010). Organotransition metal chemistry: from bonding to catalysis. Sausalito, Calif: University Science Books. ISBN   978-1-891389-53-5. OCLC   310401036.
  2. ↑ Beckhaus, Rüdiger; Sang, Javier; Oster, Jürgen; Wagner, Trixie (1994). "Zum reaktionsverhalten eines Vinylidentitanocen-Intermediates gegenüber protischen Agenzien—selektive Synthesen von 1-Alkenyltitanocenverbindungen". Journal of Organometallic Chemistry. 484 (1–2): 179–190. doi:10.1016/0022-328X(94)87203-1.
  3. ↑ Evans, Kieren J.; Morton, Paul A.; Luz, Christian; Miller, Callum; Raine, Olivia; Lynam, Jason M.; Mansell, Stephen M. (2021). "Rhodium Indenyl NHC and Fluorenyl-Tethered NHC Half-Sandwich Complexes: Synthesis, Structures and Applications in the Catalytic C−H Borylation of Arenes and Alkanes". Chemistry – A European Journal. 27 (71): 17824–17833. doi:10.1002/chem.202102961. PMC   9299238 . PMID   34653269.
  4. ↑ Frohnapfel, David S.; Templeton, Joseph L. (2000). "Transition metal η2-vinyl complexes". Coordination Chemistry Reviews. 206–207: 199–235. doi:10.1016/s0010-8545(00)00269-1.
  5. ↑ Jutand, Anny; Négri, Serge (2003). "Rate and Mechanism of the Oxidative Addition of Vinyl Triflates and Halides to Palladium(0) Complexes in DMF". Organometallics. 22 (21): 4229–4237. doi:10.1021/om030298c.
  6. ↑ Zhen, Hongshi; Wang, Chunming; Hu, Yonghan; Flood, Thomas C. (1998). "Reactions of (Trimethyltriazacyclononane)Rh(vinyl)3, −Rh( Z -propenyl)3, and −Rh(vinyl)2Me with Protic Acids. The Relative Migratory Aptitude of Methyl and Vinyl Groups to an (Ethylidene)Rh Alkylidene Carbon". Organometallics. 17 (24): 5397–5405. doi:10.1021/om980423y.
  7. ↑ Kusy, Rafał; Grela, Karol (2025). "Renaissance in Alkyne Semihydrogenation: Mechanism, Selectivity, Functional Group Tolerance, and Applications in Organic Synthesis". Chemical Reviews. 125 (9): 4397–4527. doi:10.1021/acs.chemrev.4c00001. PMID   40279298.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.