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Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage

Peters, Jonas C. and Johnson, Adam R. and Odom, Aaron L. and Wanandi, Paulus W. and Davis, William M. and Cummins, Christopher C. (1996) Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage. Journal of the American Chemical Society, 118 (42). pp. 10175-10188. ISSN 0002-7863. doi:10.1021/ja960564w.

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Three-coordinate Ti(NRAr)_3 [R = C(CD_3)_2(CH_3), Ar = C_6H_3Me_2] was prepared in 73% yield by sodium amalgam reduction of ClTi(NRAr)_3 and in 83% yield upon treatment of TiCl_3(THF)_3 with 3 equiv of Li(NRAr)(OEt_2) in the presence of TMEDA. Ti(^tBuNPh)_3 was prepared similarly in 75% yield by treatment of TiCl_3(THF)_3 with 3 equiv of Li(^tBuNPh)(OEt_2) in the presence of TMEDA. Reaction of Ti(NRAr)_3 with NMo(O^tBu)_3 in hydrocarbon solvents at −35 °C generates a thermally unstable intermediate formulated as (^tBuO)_3Mo[μ-N]Ti(NRAr)_3, which readily loses a tert-butyl radical and isomerizes at 25 °C. Kinetics of the latter process were obtained over the temperature range 20−60 °C; the process exhibits clean first-order behavior. The following activation parameters were obtained:  ΔH⧧ = 21.4 ± 0.2 kcal mol^(-1) and ΔS⧧ = −3.7 ± 0.6 cal mol^(-1) K^(-1). The oxo-bridged product (^tBuO)_2(N)Mo[μ-O]Ti(NRAr)_3 was isolated in 83% yield from this reaction. Full characterization of the latter diamagnetic complex included an X-ray crystal structure and an ^(15)N NMR study. Ti(NRAr)_3 (1 equiv) reacts further with (^tBuO)_2(N)Mo[μ-O]Ti(NRAr)_3 to generate a species formulated as a second paramagnetic nitrido-bridged intermediate, (^tBuO)_2Mo{[μ-O]Ti(NRAr)_3}{[μ-N]Ti(NRAr)_3}, which at 25 °C loses a tert-butyl radical and isomerizes to give the final product, (^tBuO)(N)Mo{[μ-O]Ti(NRAr)_3}_2, isolated as an orange powder in 91% yield. Characterization of the latter diamagnetic complex included an ^(15)N NMR study. Attempts to displace a third tert-butyl radical by treatment of (^tBuO)(N)Mo{[μ-O]Ti(NRAr)_3}_2 with Ti(NRAr)_3 led to no reaction. Treatment of (^tBuO)(N)Mo{[μ-O]Ti(NRAr)_3}_2 with neat methyl iodide led to the isolation of (MeO)(N)Mo{[μ-O]Ti(NRAr)_3}_2 in 51% yield; ^(13)C and nitrido-^(15)N derivatives of this species were prepared for spectroscopic characterization. O_2Mo{[μ-O]Ti(^tBuNPh)_3}_2 was prepared in 59% yield upon treatment of MoO_2(O^tBu)_2 with 2 equiv of Ti(^tBuNPh)_3 in benzene at 65 °C. Full characterization of O_2Mo{[μ-O]Ti(^tBuNPh)_3}_2 included a single-crystal X-ray diffraction study. Previously reported (^iPrO)_3V[μ-O]Ti(NRAr)_3 was oxidized with ferrocenium triflate to give TfOTi(NRAr)_3 and OV(O^iPr)_3. TfOTi(NRAr)_3 was prepared independently in 80% yield by treatment of Ti(NRAr)_3 with ferrocenium triflate. (^iPrO)_3V[μ-O]Ti(NRAr)_3 is stable in the presence of methyl iodide. ITi(NRAr)_3 was prepared independently by treatment of Ti(NRAr)_3 with the stoichiometric amount of iodine. Paramagnetic (^tBuO)_3V[μ-O]Ti(NRAr)_3 was prepared as orange-brown needles in 94% yield and was found to be thermally stable. The relatively robust μ-nitrido compound (Me_2N)_3Mo[μ-N]Ti(^tBuNPh)_3, which was prepared in 77% isolated yield, showed no decomposition when heated in benzene at 70 °C for 13 h.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle Information
Peters, Jonas C.0000-0002-6610-4414
Johnson, Adam R.0000-0002-7407-0533
Additional Information:© 1996 American Chemical Society. Received February 21, 1996. Publication Date (Web): October 23, 1996. For funding, C.C.C. thanks the National Science Foundation (CAREER Award CHE-9501992), DuPont (Young Professor Award), the Packard Foundation (Packard Foundation Fellowship), Union Carbide (Innovation Recognition Award), and 3M (Innovation Fund Award). J.C.P. is grateful for a Department of Defense graduate research fellowship.
Funding AgencyGrant Number
DuPont Young Professor AwardUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Union Carbide Innovation Recognition AwardUNSPECIFIED
Department of Defense (DOD) Graduate Research FellowshipUNSPECIFIED
Issue or Number:42
Record Number:CaltechAUTHORS:20141204-145154416
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Official Citation:Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage Jonas C. Peters,Adam R. Johnson,Aaron L. Odom,Paulus W. Wanandi,William M. Davis, and, and Christopher C. Cummins Journal of the American Chemical Society 1996 118 (42), 10175-10188
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52407
Deposited By: Tony Diaz
Deposited On:04 Dec 2014 23:16
Last Modified:10 Nov 2021 19:40

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