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Download fileSyntheses of Molybdenum Oxo Benzylidene Complexes
dataset
posted on 2018-10-08, 00:00 authored by Feng Zhai, Konstantin V. Bukhryakov, Richard R. Schrock, Amir H. Hoveyda, Charlene Tsay, Peter MüllerThe reaction between
Mo(O)(CHAro)(ORF6)2(PMe3) (Aro = ortho-methoxyphenyl,
ORF6 = OCMe(CF3)2) and 2 equiv of
LiOHMT (OHMT = O-2,6-(2,4,6-Me3C6H2)2C6H3) leads to Mo(O)(CHAro)(OHMT)2, an X-ray structure
of which shows it to be a trigonal bipyramidal anti benzylidene complex in which the o-methoxy oxygen
is coordinated to the metal trans to the apical oxo
ligand. Addition of 1 equiv of water (in THF) to the benzylidyne complex,
Mo(CArp)(OR)3(THF)2 (Arp = para-methoxyphenyl, OR = ORF6 or OC(CF3)3 (ORF9)) leads to formation of {Mo(CArp)(OR)2(μ-OH)(THF)}2(μ-THF)
complexes. Addition of 1 equiv of a phosphine (L) to Mo(CArp)(ORF9)3(THF)2 in THF, followed
by addition of 1 equiv of water, all at room temperature, yields Mo(O)(CHArp)(ORF9)2(L) complexes in good
yields for several phosphines (e.g., PMe2Ph (69% by NMR),
PMePh2 (59%), PEt3 (69%), or P(i-Pr)3 (65%)). The reaction between Mo(O)(CHArp)(ORF9)2(PEt3) and 2 equiv
of LiOHMT proceeds smoothly at 90 °C in toluene to give Mo(O)(CHArp)(OHMT)2, a four-coordinate syn alkylidene complex. Mo(O)(CHArp)(OHMT)2 reacts with ethylene (1 atm in C6D6) to give
(in solution) a mixture of Mo(O)(CHArp)(OHMT)2, Mo(O)(CH2)(OHMT)2, and an unsubstituted
square pyramidal metallacyclobutane complex, Mo(O)(CH2CH2CH2)(OHMT)2, along with
ethylene and ArpCHCH2. Mo(O)(CHArp)(OHMT)2 also reacts with 2,3-dicarbomethoxynorbornadiene
to yield syn and anti isomers of
the “first-insertion” products that contain a cis CC bond.
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