Zirconium Complexes Supported by Imidazolones: Synthesis, Characterization, and Application of Precatalysts for the Hydroamination of Aminoalkenes
摘要:
Dimeric zirconium benzyl and amide complexes supported by an imidazolone framework have been successfully synthesized and fully characterized. The amide complexes were found to be effective catalysts for intramolecular hydroamination of primary and secondary amines.
Metal and halogen dependence of the rate effect in hydroamination/cyclization of unactivated aminoalkenes: Synthesis, characterization, and catalytic rates of CCC-NHC hafnium and zirconium pincer complexes
作者:Wesley D. Clark、Joon Cho、Henry U. Valle、T. Keith Hollis、Edward J. Valente
DOI:10.1016/j.jorganchem.2013.11.001
日期:2014.2
(2c) was reacted with a stoichiometric amount of Zr(NMe2)4 or Hf(NMe2)4 yielding four new early transition metal CCC-N-heterocylic carbene (CCC-NHC) pincer complexes. Two of the CCC-NHC pincer complexes were synthesized via a new methodology, which allowed for a room temperature reaction, shorter reaction times, and slightly less Zr(NMe2)4 or Hf(NMe2)4. The molecular structure of 2-(1,3-bis-3′-butyl
CCC–N-heterocyclic carbene pincer complexes: Synthesis, characterization and hydroamination activity of a hafnium complex
作者:Joon Cho、T. Keith Hollis、Edward J. Valente、Jaclyn M. Trate
DOI:10.1016/j.jorganchem.2010.10.004
日期:2011.1
Our methodology for the stoichiometric preparation of CCC–NHC pincer complexes of Zr has been extended to Hf. The CCCBu–NHC pincer Hf complex has been characterized by X-ray crystal structure analysis. Catalytic activity in the intramolecular hydroamination/cyclization of unactivated alkenes is reported and compared to the recently reported Zr analog. An improved, scaled-up CuO-catalyzed aryl amination
An improved method for the synthesis of zirconium (CCC-N-heterocyclic carbene) pincer complexes and applications in hydroamination
作者:Joon Cho、T. Keith Hollis、Theodore R. Helgert、Edward J. Valente
DOI:10.1039/b805174g
日期:——
Upon heating Zr(NMe2)4, 1,3-bis(N-butyl-imidazolium)benzene diiodide and toluene analytically pure Zr pincer complex was obtained, which was found to be an intramolecular hydroamination catalyst.
Extreme π-Loading as a Design Element for Accessing Imido Ligand Reactivity. A CCC-NHC Pincer Tantalum Bis(imido) Complex: Synthesis, Characterization, and Catalytic Oxidative Amination of Alkenes
作者:Theodore R. Helgert、Xiaofei Zhang、Hannah K. Box、Jason A. Denny、Henry U. Valle、Allen G. Oliver、Gopalakrishna Akurathi、Charles Edwin Webster、T. Keith Hollis
DOI:10.1021/acs.organomet.6b00216
日期:2016.10.24
A rare Ta bis(imido) complex, which has unique reactivity, was prepared by manipulating the coordination sphere of a CCC-NHC pincer Ta complex. The reaction of lithium tert-butylamide with complex 1 yielded (1,3-bis(3'-butylimidazol-2'-yl-1'-idene)-2-phenylene)bis(tert-butylimido)tantalum(V) (2) as a lithium iodide bridged dimer, as determined by the X-ray structure. Complex 2 catalytically cyclized alpha,omega-aminoalkenes to effect an oxidative amination of alkenes (dehydrogenation by C-H activation) and produced a cyclic imine, an equivalent of reduced substrate, and varying proportions of hydroamination. Various additives and concentration impact the catalytic results. Computational and experimental observations have led to an initial mechanistic hypothesis. Based upon it, precatalyst 2 appears to be the first example of a bifunctional catalyst (MH-NHR) that is highly selective for nonpolar C-C bonds in preference to polar C-X bonds for outer-sphere hydrogenation.
β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination
作者:Naresh Eedugurala、Zhuoran Wang、KaKing Yan、Kasuni C. Boteju、Umesh Chaudhary、Takeshi Kobayashi、Arkady Ellern、Igor I. Slowing、Marek Pruski、Aaron D. Sadow
DOI:10.1021/acs.organomet.6b00956
日期:2017.3.27
A series of homoleptic rare-earth silazido compounds and their silica-grafted derivatives were prepared to compare spectroscopic and catalytic features under homogeneous and interfacial conditions. Trivalent tris(silazido) compounds LnN(SiHMe2)tBu}(3) (Ln = Sc (1), Y (2), Lu (3)) are prepared in high yield by salt metathesis reactions. Solution-phase and solid-state characterization of 1-3 by NMR and IR spectroscopy and X-ray diffraction reveals Ln-H-Si interactions. These features are retained in solvent coordinated 2 center dot Et2O, 2 center dot THF, and 3 center dot THF. The change in spectroscopic features characterizing the secondary interactions (v(s1H), (1)J(siH)) from the unactivated SiH in the silazane HN(SiHMe2)tBu follows the trend 3 > 2 > 1 approximate to 2 center dot THF approximate to 3 center dot THF. Ligand lability follows the same pattern, with Et2O readily dissociating from 2 center dot Et2O while THF is displaced only during surface grafting reactions. I and 2 center dot THF graft onto mesoporous silica nanoparticles (MSN) to give LnN(SiHMe2)tBu}(n)@MSN (Ln = Sc (1@MSN), Y (2@MSN)) along with THF and protonated silazido as HN(SiHMe2)tBu and H(2)NtBu. The surface species are characterized by multinuclear and multidimensional solid-state (SS) NMR spectroscopic techniques, as well as diffuse reflectance FTIR, elemental analysis, and reaction stoichiometry. A key (1)J(SiH) SSNMR measurement reveals that the grafted sites most closely resemble Ln.THF adducts, suggesting that siloxane coordination occurs in grafted compounds. These species catalyze the hydroamination/bicyclization of aminodialkenes, and both solution-phase and interfacial conditions provide the bicyclized product with equivalent cis:trans ratios. Similar diastereoselectivities mediated by catalytic sites under the two conditions suggest similar effective environments.