Synthesis of Molybdenum and Tungsten Alkylidene Complexes that Contain a <i>tert</i>-Butylimido Ligand
作者:Hyangsoo Jeong、Richard R. Schrock、Peter Müller
DOI:10.1021/acs.organomet.5b00633
日期:2015.9.14
A variety of molybdenum or tungsten complexes that contain a tert-butylimido ligand have been prepared. For example, the o-methoxybenzylidene complex W(N-t-Bu) ( CH-o-MeOC6H4) (C1)(2)(py) was prepared through addition of pyridinium chloride to W(N-t-Bu)(2)-(CH2-o-MeOC6H4)(2), while Mo(N-t-Bu)(CH-o-MeOC6H4)(ORF)(2)(tBuNI-12) complexes (ORF = 006F(3) or OC(CF3)(3)) were prepared through addition of two equivalents of RFOH to mo(N-t-Bu)(2)(CH2-o-MeOC6H4)(2). An X-ray crystallographic study of Mo(N-t-Bu)(CH-o-MeOC6H4)[0C(CF3)(3)]2(t-BuNH2) showed that the methoxy oxygen is bound to the metal and that two protons on the tert-butylamine ligand are only a short distance away from one of the CF3 groups on one of the perfluoro-tert-butoxide ligands (H center dot center dot center dot F = 2.456(17) and 2.467(17) A). Other synthesized tungsten tert-butylimido complexes include W(N-t-Bu) (CH-o-MeOC6H4)(pyr)(2)(2,21-bip-yridine) (pyr = pyrrolide), W(N-t-Bu) (CH-o-MeOC6H,t)(pyr)(OHMT) (OHMT = 0-2,6-(mesity1)(2)C6H3), W(N-t-Bu) (CH-t-Bu) (OH_MT)(C1)(py) (py = pyridine), W(N-t-Bu) (CH-t-Bu) (OHMT)(Cl), W(N-t-Bu) (CH-t-Bu)(PYr)(0DFT)(PY), W(N-t-Bu) (CH-t-Bu)(OHMT)(2), and W(N-t-Bu) (CH-t-Bu) (ODFT)(2) (ODFT = 0-2,6- (C6F5)(2)C6H3). Interestingly, W(N-t-Bu)(CH-t-Bu)(OHMT)(2) does not react with ethylene or 2,3-dicarbomethoxynorbomadiene. Removal of pyridine from W(N-t-Bu) (CH-t-Bu)(Biphencp3)(pyridine) (Biphencp3 = 3,3'di-tert-buty1-5,5'-bistrifluoromethy1-6,6'-dimethyl-1,1'-biphenyl-2,2'-diolate) with B(C6F5)(3) led to formation of a five-coordinate 14e neopentyl complex as a consequence of CH activation in one of the methyl groups in one tert-butyl group of the Biphenc F-3 ligand, as was proven in an X-ray study. An attempted synthesis of W(N-t-Bu) (CH-t-Bu)(Biphenme) (Biphenme = 3,3'-di-tertbuty1-5,5',6,6'-tetramethy1-1,1'-biphenyl-2,2'-diolate) led to formation of a 1:1 mixture of W(N-t-Bu)(CH-t-Bu)(Biphenme) and a neopentyl complex analogous to the one characterized through an X-ray study. The metallacyclobutane complexes W(N-t-Bu) (C3H6)(Pyrrolide)(0DFT) and W(N-t-Bu) (C3H6) (ODFT)(2) were prepared in reactions involving W(N-t-Bu)(CH-tBu)(pYr)(2)(biPY), ZnC12(dioxane), and one or two equivalents of DFTOH, respectively, under 1 atm of ethylene.