153483-75-1Relevant academic research and scientific papers
Reaction of neopentylidene complexes of the type M(CH-t-Bu)(N-2,6-C6H3-i-Pr2)(OR)2 (M = W, Mo) with methyl acrylate and N,N-dimethylacrylamide to give metallacyclobutane complexes
Feldman, Jerald,Murdzek, John S.,Davis, William M.,Schrock, Richard R.
, p. 2260 - 2265 (1989)
W(CH-t-Bu)(NAr)[OCMe2(CF3)]2 (Ar = 2,6-C6H3-i-Pr2) reacts with methyl acrylate to give the metallacyclobutane complex W[CH(t-Bu)CH2CH(CO2Me)](NAr)[OCMe2(CF 3)]2 (1). 1 belongs to the space group P21/c with a = 17.323 (3) ?, b = 10.408 (3) ?, c = 18.758 (3) ?, V = 3337 (2) ?3, Mr = 769.52, ρ(calcd) = 1.531 g cm-3, Z = 4, and μ = 37.33 cm-1 (R = 0.043, Rw = 0.043). The complex has an approximately square-pyramidal core geometry with the carbonyl oxygen atom bound weakly trans to the apical imido ligand. The four basal sites are occupied by the two alkoxide oxygen atoms and the two α-carbon atoms of the metallacyclobutane ligand. Similar reactions may be carried out between M(CH-t-Bu) (NAr)-[OCMe2(CF3)]2 or M(CH-t-Bu)(NAr)(O-t-Bu)2 and N,N-dimethylacrylamide to give metallacyclobutane complexes of the type M[CH(t-Bu)CH2CH(CONMe2)](NAr)(OR)2 (OR = OCMe2(CF3), O-t-Bu; M = W, Mo). 1 reacts with trimethylphosphine to give W(CH-t-Bu)(NAr)[OCMe2(CF3)]2(PMe3), but complexes of the type W[CH(t-Bu)CH2CH(CONMe2)](NAr)(OR)2 (OR = OCMe2(CF3), O-t-Bu) do not react readily with trimethylphosphine. Differences in reactivity of the methyl acrylate and the dimethylacrylamide tungsten complexes with ethylene are analogous. In contrast, Mo[CH(t-Bu)CH2CH(CONMe2)](NAr)(O-t-Bu)2 is in equilibrium with Mo(CH-t-Bu)(NAr)(O-t-Bu)2 and free N,N-dimethylacrylamide in solution.
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.
Well-characterized olefin metathesis catalysts that contain molybdenum
Murdzek, John S.,Schrock, Richard R.
, p. 1373 - 1374 (2008/10/08)
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)(dme)Cl2 (1), which upon treatment with a catalytic amount of NEt3 is transformed into Mo(CH-t-Bu)(NAr)(dme)Cl2 (2) virtually quantitatively. Complexes of the type Mo(CH-t-Bu)-(NAr)(OR)2 (OR = OCMe(CF3)2, OCMe2(CF3), or OCMe3) have been prepared. Mo(CH-t-Bu)(NAr)[OCMe(CF3)2]2 is an active metathesis catalyst (but less active than the tungsten analogue) while Mo(CH-t-Bu)(NAr)(OCMe3)2 does not react with ordinary olefins. Addition of Me3SiCH=CH2 to Mo(CH-t-Bu)(NAr)[OCMe(CF3)2]2 to yield Mo-(CHSiMe3)(NAr)[OCMe(CF3)2]2 is taken as evidence that molybdacyclobutane complexes lose an olefin more readily than analogous tungstacyclobutane complexes.
