108945-98-8Relevant articles and documents
Diphenylamido precursors to bisalkoxide molybdenum olefin metathesis catalysts
Sinha, Amritanshu,Schrock, Richard R.,Mueller, Peter,Hoveyda, Amir H.
, p. 4621 - 4626 (2008/10/09)
We have found that Mo(NAr)(CHR′)(NPh2)2 (R′ = t-Bu or CMe2Ph) and Mo(NAr′)(CHCMe 2Ph)-(NPh2)2 (Ar = 2,6-i-Pr2C 6H3; Ar′ = 2,6-Me2C6H 3) can be prepared through addition of 2 equiv of LiNPh2 to Mo(NR″)(CHR′)(OTf)2(dme) species (R″ = Ar or Ar′, dme = 1,2-dimethoxyethane), although yields are low. A high-yield route consists of addition of LiNPh2 to bishexafluro-tert-butoxide species. An X-ray structure of Mo(NAr)(CHCMe2Ph)(NPh 2)2 reveals that the two diphenylamido groups are oriented in a manner that allows an 18-electron count to be achieved. The diphenylamido complexes react readily with t-BuOH and (CF3)2MeCOH, but not readily with the sterically demanding biphenol H2[Biphen] (Biphen2- = 3,3′-di-tert-butyl-5,5′,6,6′- tetramethyl-1,1′-biphenyl-2,2′-diolate). The diphenylamido complexes do react with various 3,3′-disubstituted binaphthols to yield binaphtholate catalysts that can be prepared in situ and employed for a simple asymmetric ring-closing metathesis reaction. In several cases conversions and enantioselectivities were comparable to reactions in which isolated catalysts were employed.
Synthesis of molybdenum imido alkylidene complexes and some reactions involving acyclic olefins
Schrock, Richard R.,Murdzek, John S.,Bazan, Gui C.,Robbins, Jennifer,DiMare, Marcello,O'Regan, Marie
, p. 3875 - 3886 (2007/10/02)
The reaction between Mo(C-t-Bu)(dme)Cl3 (dme = 1,2-dimethoxyethane) and Me3SiNHAr (Ar = 2,6-diisopropylphenyl) yields Mo(C-t-Bu)(NHAr)Cl2(dme) (1), which upon treatment with a catalytic amount Of NEt3 is transformed into Mo(CH-t-Bu)(NAr)Cl2(dme) (2). Complexes of the type Mo(CH-t-Bu)(NAr)(OR)2 (OR = OCMe(CF3)2, OCMe2(CF3), O-t-Bu, or OAr) have been prepared from 2. Complexes of the type Mo(C-t-Bu)(NHAr)(OR)2 (OR = OCMe(CF3)2 or OAr) have been prepared from 1, but they cannot be transformed into Mo(CH-t-Bu)(NAr)(OR)2 complexes. A precursor to imido alkylidene complexes that is related to 2 has been prepared by the sequence MoO2 → MoO2Cl2 → Mo(NAr)2Cl2 → Mo-(NAr)2(CH2R′)2 → Mo(CHR′)(NAr)(OTf)2(dme) (R′ = t-Bu or CMe2Ph; OTf = OSO2CF3). Mo(CH-t-Bu)(NAr)(OTf)2(dme) crystallizes in the space group P1 with a = 17.543 ?, b = 19.008 ?, c = 9.711 ?, α = 91.91°, β = 99.30°, γ = 87.27°, Z = 4, Mr = 729.60, V = 3191.1 ?3, ρ(calcd) = 1.518 g cm-3. It is a pseudooctahedral species in which the imido and alkylidene ligands are cis to one another, the triflate ligands are mutually trans, and the tert-butyl group points toward the imido ligand (syn orientation). Neophylidene complexes, Mo(CHCMe2Ph)(NAr)(OR)2 (OR = O-t-Bu, OAr, or O-2-C6H4-t-Bu), have been prepared from Mo(CHCMe2Ph)(NAr)(triflate)2(dme). Activity for the metathesis of cis-2-pentene by Mo(CHR′)-(NAr)(OR)2 complexes roughly correlates with the electron-withdrawing ability of OR, being rapid when OR = OCMe(CF3)2 and slow to negligible when OR = O-t-Bu. In several cases it is clear from proton NMR studies that the alkylidene ligand can rotate on the NMR time scale; in Mo(CHSiMe3)(NAr)(OAr)2 it has been shown that ΔG?298 = 16.0 kcal mol-1 for this process. Mo[CH(SiMe3)CH(SiMe3)CH2](NAr)[OCMe 2(CF3)]2 has been observed and found to be ～3 orders of magnitude less stable than the analogous tungsten complex. Trigonal-bipyramidal Mo(CH2CH2CH2)(NAr)[OCMe(CF3) 2]2 can be prepared at 25 °C in high yield, but it decomposes over a period of 12 h. Instability of OCMe(CF3)2 metallacyclobutane complexes has been traced to reduction by β-hydride rearrangement to give an olefin. In one case a complex containing the olefin product, Mo(NAr)(Me3SiCH=CH2)[OCMe(CF3)2] 2, was isolated.
