Chemistry of compounds containing a carbon-to-tantalum bond
Tantalum-Carbon Bond
Organotantalum chemistry is the chemistry of chemical compounds containing a carbon-to-tantalumchemical bond. A wide variety of compound have been reported, initially with cyclopentadienyl and CO ligands. Oxidation states vary from Ta(V) to Ta(-I).
Salts of [Ta(CH3)6]− are prepared by alkylation of TaF5 using methyl lithium:[2]
TaF5 + 6 LiCH3 → Li[Ta(CH3)6] + 5 LiF
Alkylidene complexes
Tantalum alkylidene complexes arise by treating trialkyltantalum dichloride with alkyl lithium reagents. This reaction initially forms a thermally unstable tetraalkyl-monochloro-tantalum complex, which undergoes α-hydrogen elimination, followed by alkylation of the remaining chloride.[1]
Synthesis of Tantalum Monoalkylidene Complexes
Tantalum alkylidene complexes are nucleophilic.[1] They effect a number of reactions including: olefinations, olefin metathesis, hydroaminoalkylation of olefins, and conjugate allylation of enones.
Reduction of TaCl5 under an atmosphere of CO gives the salts of [Ta(CO)6]−.[5] These same anions can be obtained by carbonylation of tantalum arene complexes.
A number of tantalum isocyanide complexes are also known.[6]
Tantalum-alkyne complexes[8] catalyze cyclotrimerizations.[9][10] Some tantalum-alkyne complexes are precursors to allylic alcohols.[11] Tantalacyclopropenes are invoked as intermediates.
Utimoto's Synthesis of (E)-Allylic Alcohols
Tantalum-amido complexes
Organotantalum compounds are invoked as intermediates in C-alkylation of secondary amines with 1-alkenes using Ta(NMe2)5.[12] The chemistry developed by Maspero was later brought to fruition when Hartwig and Herzon reported the hydroaminoalkylation of olefins to form alkylamines:[13]
Organotantalum reagents arise via transmetalation of organotin compounds with tantalum(V) chloride.[17] These organotantalum reagents promote the conjugate allylation of enones. Although the direct allylation of carbonyl groups is prevalent throughout the literature, little has been reported on the conjugate allylation of enones.[18]
Applications
Organotantalum compounds are of academic interest, but few or no commercial applications have been described.
References
^ abcSchrock, Richard R. (1979-03-01). "Alkylidene complexes of niobium and tantalum". Accounts of Chemical Research. 12 (3): 98–104. doi:10.1021/ar50135a004. ISSN0001-4842.
^McLain, S. J.; Wood, C. D.; Schrock, R. R. (1977-05-01). "Multiple metal-carbon bonds. 6. The reaction of niobium and tantalum neopentylidene complexes with simple olefins: a route to metallocyclopentanes". Journal of the American Chemical Society. 99 (10): 3519–3520. doi:10.1021/ja00452a064. ISSN0002-7863.
^Endy Y.-J. Min; John E. Bercaw (2014). "Bis(η 5 -Pentamethylcyclopentadienyl) Complexes of Niobium and Tantalum". Inorganic Syntheses: Volume 36. Vol. 36. pp. 52–57. doi:10.1002/9781118744994.ch11. ISBN978-1-118-74499-4. {{cite book}}: |journal= ignored (help)
^J. E. Ellis; A. Davison (1976). "Tris[Bis(2-Methoxyethyl)Ether]Potassium and Tetraphenylarsonium Hexacarbonylmetallates(1-) of Niobium and Tantalum". Tris[Bis(2-Methoxyethyl)Ether]Potassium and Tetraphenylarsonium Hexacarbonylmetallates(1–) of Niobium and Tantalum. Inorganic Syntheses. Vol. 16. pp. 68–73. doi:10.1002/9780470132470.ch21. ISBN978-0-470-13247-0.
^Brennessel, William W.; Romanenkov, Alexander; Young, Victor G.; Ellis, John E. (2019). "Tantalum isocyanide complexes: TaI(CNDipp)6 (Dipp is 2,6-diisopropylphenyl) and ionic [Ta(CNDipp)7][Ta(CNDipp)6], a formal disproportionation product of the 17-electron Ta0 metalloradical Ta(CNDipp)6". Acta Crystallographica Section C: Structural Chemistry. 75 (2): 135–140. doi:10.1107/S2053229619000834. PMID30720451. S2CID73450348.
^Pampaloni, G. (2010). "Aromatic hydrocarbons as ligands. Recent advances in the synthesis, the reactivity and the applications of bis(η6-arene) complexes". Coordination Chemistry Reviews. 254 (5–6): 402–419. doi:10.1016/j.ccr.2009.05.014.
^Labinger, Jay A.; Schwartz, Jeffrey; Townsend, John M. (1974-06-01). "Iodo- and hydridotantalum(III) complexes of dialkylacetylenes". Journal of the American Chemical Society. 96 (12): 4009–4011. doi:10.1021/ja00819a047. ISSN0002-7863.
^Cotton, F. Albert; Hall, William T. (1979-08-01). "Reactions of tantalum(III) with alkynes and nitriles". Journal of the American Chemical Society. 101 (17): 5094–5095. doi:10.1021/ja00511a064. ISSN0002-7863.
^Bruck, M. A.; Copenhaver, A. S.; Wigley, D. E. (1987-10-01). "Alkyne cyclizations at reduced tantalum centers: synthesis and molecular structure of (.eta.6-C6Me6)Ta(O-2,6-i-Pr2C6H3)2Cl". Journal of the American Chemical Society. 109 (21): 6525–6527. doi:10.1021/ja00255a056. ISSN0002-7863.
^Takai, Kazuhiko; Kataoka, Y.; Utimoto, K. (1990-03-01). "Tantalum-alkyne complexes as synthetic intermediates. Stereoselective preparation of trisubstituted allylic alcohols from acetylenes and aldehydes". The Journal of Organic Chemistry. 55 (6): 1707–1708. doi:10.1021/jo00293a008. ISSN0022-3263.
^Eisenberger, Patrick; Ayinla, Rashidat O.; Lauzon, Jean Michel P.; Schafer, Laurel L. (2009-10-19). "Tantalum–Amidate Complexes for the Hydroaminoalkylation of Secondary Amines: Enhanced Substrate Scope and Enantioselective Chiral Amine Synthesis". Angewandte Chemie International Edition. 48 (44): 8361–8365. doi:10.1002/anie.200903656. ISSN1521-3773. PMID19787670.
^Dörfler, Jaika; Doye, Sven (2014-05-01). "A Commercially Available Tantalum Catalyst for the Highly Regioselective Intermolecular Hydroaminoalkylation of Styrenes". European Journal of Organic Chemistry. 2014 (13): 2790–2797. doi:10.1002/ejoc.201400082. ISSN1099-0690.
^Payne, Philippa R.; Garcia, Pierre; Eisenberger, Patrick; Yim, Jacky C.-H.; Schafer, Laurel L. (2013-05-03). "Tantalum Catalyzed Hydroaminoalkylation for the Synthesis of α- and β-Substituted N-Heterocycles". Organic Letters. 15 (9): 2182–2185. doi:10.1021/ol400729v. ISSN1523-7060. PMID23600625.
