On Feb 14, 2022, at 12:12 PM, Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU> wrote:
As long as activists waste their time, energy, and money banning individual bad-actor chemicals,
R1 is selected from the group consisting of an alkyl having 1 to 20 carbon atoms, an aryl having 6 to 20 carbon atoms, an aralkyl having 7 to 30 carbon atoms, halogen substituted derivative of each and silicon-containing analogs of each; R2 is selected from the group consisting of R1 or is a substituent resulting from the reaction of the Re=CHR2 moiety of the compound with an olefin that is being metathesized;Examples of R1 and R2 include but are not limited to phenyl, t-butyl, 1bethyl-1-phenyl-ethyl, trimethylsilyl, triphenyl, methyl, triphenylsilyl, tri-t-butyl, tri-t-butylsilyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl and 2,6-dimethylphenyl.
R3 and R4 are individually selected from groups consisting of R1, a halogen, triflate, and concatenated combinations of R3 and R4, wherein R3 and R4 individually may contain alkoxide oxygen atoms which are bound to the rhenium atom; n is a positive integer (preferably one or two); and provided that when R1 and R2 are t-butyl and R3 and R4 are the same, then R3 and R4 are groups other than t-butoxide, trimethylsiloxide, neopentyl or a halogen.The remaining two ligands (R3 and R4) can be any substituent which is sufficiently electron withdrawing enough to render the complex active (i.e., render the rhenium atom sufficiently electrophilic) for metathesis reactions. While it is preferable that both ligands are electron withdrawing, the compounds of this invention may contain only one electron withdrawing ligand which is sufficiently strong enough to render the complex active for metathesis.Preferably, R3 and R4 are both alkoxide ligands in which the alcohol corresponding to the electron withdrawing alkoxide ligands should have a pKa of about 9 or below. Suitable electron withdrawing ligands which fall within this range include phenoxide, hexafluoro-t-butoxide and diisopropylphenoxide. Other examples of preferred electron withdrawing ligands include alkoxides containing 2,6-dimethylphenyl. 2,4,6-trimethylphenyl, 2,6-diisopropylphenyl, pentafluoro, phenyl, 1-methyl-1-phenyl-ethyl, 2,6-dichlorophenyl, perchlorophenyl, triphenylmethyl, triphenylsilyl, tri-t-butylsilyl, perfluoro-2-methyl-2-pentyl, trifluoro-t-butyl (CF3 (CH3)2 C), hexafluoro-t-butyl ((CF3)2 CH3 C) and perfluoro-t-butyl. Examples of concatenated R3 and R4groups are pinacolate, 2.6-dimethyl-2,6-heptanediolate and propan-1,3-diolate.
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