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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. https://resolver.caltech.edu/CaltechAUTHORS:20141204-145154416

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Abstract

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
http://dx.doi.org/10.1021/ja960564w DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja960564wPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/ja960564wPublisherSupporting Information
ORCID:
AuthorORCID
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.
Funders:
Funding AgencyGrant Number
NSFCHE-9501992
DuPont Young Professor AwardUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Union Carbide Innovation Recognition AwardUNSPECIFIED
3M CorporationUNSPECIFIED
Department of Defense (DOD) Graduate Research FellowshipUNSPECIFIED
Issue or Number:42
DOI:10.1021/ja960564w
Record Number:CaltechAUTHORS:20141204-145154416
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141204-145154416
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
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Dec 2014 23:16
Last Modified:10 Nov 2021 19:40

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