| Abstract
| - Three-coordinate Ti(NRAr)3 [R =C(CD3)2(CH3), Ar =C6H3Me2] was prepared in 73%yield by sodiumamalgam reduction of ClTi(NRAr)3 and in 83% yieldupon treatment of TiCl3(THF)3 with 3 equivof Li(NRAr)(OEt2) in the presence of TMEDA.Ti(tBuNPh)3 was prepared similarly in75% yield by treatment ofTiCl3(THF)3with 3 equiv of Li(tBuNPh)(OEt2) inthe presence of TMEDA. Reaction of Ti(NRAr)3 withNMo(OtBu)3 inhydrocarbon solvents at −35 °C generates a thermally unstableintermediate formulated as(tBuO)3Mo[μ-N]Ti(NRAr)3, which readily loses a tert-butyl radicaland isomerizes at 25 °C. Kinetics of the latter process wereobtainedover the temperature range 20−60 °C; the process exhibits cleanfirst-order behavior. The following activationparameters were obtained: ΔH⧧ = 21.4 ±0.2 kcal mol-1 andΔS⧧ = −3.7 ± 0.6 calmol-1 K-1. Theoxo-bridgedproduct(tBuO)2(N)Mo[μ-O]Ti(NRAr)3was isolated in 83% yield from this reaction. Fullcharacterization of thelatter diamagnetic complex included an X-ray crystal structure and an15N NMR study. Ti(NRAr)3 (1 equiv)reactsfurther with(tBuO)2(N)Mo[μ-O]Ti(NRAr)3to generate a species formulated as a second paramagneticnitrido-bridgedintermediate,(tBuO)2Mo{[μ-O]Ti(NRAr)3}{[μ-N]Ti(NRAr)3},which at 25 °C loses a tert-butyl radical andisomerizesto 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 15N NMRstudy. Attempts to displace a third tert-butylradicalby treatment of(tBuO)(N)Mo{[μ-O]Ti(NRAr)3}2with Ti(NRAr)3 led to no reaction. Treatment of(tBuO)(N)Mo{[μ-O]Ti(NRAr)3}2 with neatmethyl iodide led to the isolation of(MeO)(N)Mo{[μ-O]Ti(NRAr)3}2in 51% yield;13C and nitrido-15N derivatives of this specieswere prepared for spectroscopic characterization.O2Mo{[μ-O]Ti(tBuNPh)3}2 was prepared in 59%yield upon treatment ofMoO2(OtBu)2 with 2 equiv ofTi(tBuNPh)3 in benzeneat65 °C. Full characterization ofO2Mo{[μ-O]Ti(tBuNPh)3}2included a single-crystal X-ray diffraction study.Previouslyreported(iPrO)3V[μ-O]Ti(NRAr)3was oxidized with ferrocenium triflate to giveTfOTi(NRAr)3 andOV(OiPr)3.TfOTi(NRAr)3 was prepared independently in 80%yield by treatment of Ti(NRAr)3 with ferroceniumtriflate.(iPrO)3V[μ-O]Ti(NRAr)3is stable in the presence of methyl iodide.ITi(NRAr)3 was prepared independentlybytreatment of Ti(NRAr)3 with the stoichiometric amountof iodine. Paramagnetic(tBuO)3V[μ-O]Ti(NRAr)3wasprepared as orange-brown needles in 94% yield and was found to bethermally stable. The relatively robust μ-nitridocompound(Me2N)3Mo[μ-N]Ti(tBuNPh)3,which was prepared in 77% isolated yield, showed no decompositionwhenheated in benzene at 70 °C for 13 h.
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