Transition metal alkenyl complex
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]
Ligand properties
[edit]
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]
Synthesis and occurrence
[edit]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
[edit]- ^ Hartwig, John F. (2010). Organotransition metal chemistry: from bonding to catalysis. Sausalito, Calif: University Science Books. ISBN 978-1-891389-53-5. OCLC 310401036.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.