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Issue 38, 2014
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Reactivity of the uranium(IV) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates: metallo-Wittig, adduct formation, C–F bond activation, and [2 + 2]-cycloaddition reactions

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Abstract

The reactivity of the uranium(IV) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (1, BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates is reported. Reaction of 1 with benzophenone proceeds to give the metallo-Wittig terminal alkene product Ph2C[double bond, length as m-dash]C(PPh2NSiMe3)2 (2); the likely “UOCl2” byproduct could not be isolated. Addition of the bulky ketone PhCOBut to 1 resulted in loss of LiCl, coordination of the ketone, and dimerisation to give [U(BIPMTMS)(Cl)(μ-Cl){OC(Ph)(But)}]2 (3). The reaction of 1 with coumarin resulted in ring opening of the cyclic ester and a metallo-Wittig-type reaction to afford [U{BIPMTMS[C(O)(CHCHC6H4O-2)]-κ3-N,O,O′}(Cl)2(THF)] (4) where the enolate product remains coordinated to uranium. The reaction of PhCOF with 1 resulted in C–F bond activation and oxidation resulting in isolation of [U(O)2(Cl)2(μ-Cl)2{(μ-LiDME)OC(Ph)[double bond, length as m-dash]C(PPh2NSiMe3)(PPh2NHSiMe3)}2] (5) along with [U(Cl)2(F)2(py)4] (6). The reactions of 1 with tert-butylisocyanate or dicyclohexylcarbodiimide resulted in the isolation of the [2 + 2]-cycloaddition products [U{BIPMTMS[C(NBut){OLi(THF)2(μ-Cl)Li(THF)3}]-κ4-C,N,N′,N′′}(Cl)3] (7) and [U{BIPMTMS[C(NCy)2]-κ4-C,N,N′,N′′}(Cl)(μ-Cl)2Li(THF)2] (8). Complexes 2–8 have been variously characterised by single crystal X-ray diffraction, multi-nuclear NMR and FTIR spectroscopies, Evans method solution magnetic moments, variable temperature SQUID magnetometry, and elemental analyses.

Graphical abstract: Reactivity of the uranium(iv) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates: metallo-Wittig, adduct formation, C–F bond activation, and [2 + 2]-cycloaddition reactions

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Publication details

The article was received on 27 Mar 2014, accepted on 25 Apr 2014 and first published on 25 Apr 2014


Article type: Paper
DOI: 10.1039/C4DT00909F
Citation: Dalton Trans., 2014,43, 14275-14283
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    Reactivity of the uranium(IV) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates: metallo-Wittig, adduct formation, C–F bond activation, and [2 + 2]-cycloaddition reactions

    O. J. Cooper, D. P. Mills, W. Lewis, A. J. Blake and S. T. Liddle, Dalton Trans., 2014, 43, 14275
    DOI: 10.1039/C4DT00909F

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