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

© 2014 the Partner Organisations.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 Ph2CC(PPh2NSiMe3)2(2); the likely "UOCl2" byproduct could not be isolated. Addition of the bulky ketone PhCOButto 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)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.