Regioselective electrophilic substitution and addition reactions at an N-coordinated pyrrolyl ligand in (PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(NC{sub 4}H{sub 4})
- Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry
The reaction of excess pyrrolyllithium with mer-(PMe{sub 2}Ph){sub 3}ReCl{sub 3} leads to the formation of the air-stable product mer(PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(NC{sub 4}H{sub 4}) (1), which has been characterized by spectroscopic techniques and by an X-ray diffraction study. Complex 1 reacts with electrophiles to form new Re(III) complexes with regioselectively substituted pyrrolyl ligands. For example, reaction with 1 equiv of N-chlorosuccinimide forms the complex with a 3-chloropyrrolyl ligand, while reaction with excess reagent produces the 3,4-dichloropyrrolyl and 2,3,4-trichloropyrrolyl complexes. The regiochemistry of the reactions has been established from the {sup 1}H NMR data, and the structure of the dibrominated product (PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(3,4-NC{sub 4}H{sub 2}Br{sub 2}) (5) has been confirmed by X-ray diffraction. Reaction of 1 with methyl triflate produces after workup (PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(3-NC{sub 4}H{sub 3}Me) (6), and further reaction of 6 with methyl triflate yields (PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(3,4-NC{sub 4}H{sub 2}(Me){sub 2}) (7). In contrast, triflic acid protonates the pyrrolyl ligand of 1 at the {alpha}-carbon to form [(PMe{sub 2}Ph){sub 3}Cl{sub 2}Re(NC{sub 4}H{sub 5})]OTf (8), which has been isolated and identified by an X-ray diffraction study. The Michael addition of dimethyl acetylenedicarboxylate to the {beta}-carbon of the pyrrolyl ligand in 1 has also been characterized. Methods for the removal of the substituted pyrrolyl ligands from the rhenium center are described.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 354378
- Journal Information:
- Organometallics, Journal Name: Organometallics Journal Issue: 11 Vol. 18; ISSN ORGND7; ISSN 0276-7333
- Country of Publication:
- United States
- Language:
- English
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