227932-83-4Relevant articles and documents
Regioselective electrophilic substitution and addition reactions at an N-coordinated pyrrolyl ligand in (PMe2Ph)3Cl2Re(NC4H4)
DuBois, M. Rakowski,Vasquez, Lisa D.,Peslherbe,Noll
, p. 2230 - 2240 (2008/10/08)
The reaction of excess pyrrolyllithium with mer-(PMe2Ph)3ReCl3 leads to the formation of the air-stable product mer-(PMe2Ph)3Cl2Re(NC4H4) (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 1H NMR data, and the structure of the dibrominated product (PMe2-Ph)3Cl2Re(3,4-NC4H 2Br2) (5) has been confirmed by X-ray diffraction. Reaction of 1 with methyl triflate produces after workup (PMe2Ph)3Cl2Re(3-NC4H3Me) (6), and further reaction of 6 with methyl triflate yields (PMe2Ph)3Cl2Re(3,4-NC4H 2(Me)2) (7). In contrast, triflic acid protonates the pyrrolyl ligand of 1 at the α-carbon to form [(PMe2Ph)3Cl2Re(NC4H 5)]OTf (8), which has been isolated and identified by an X-ray diffraction study. The Michael addition of dimethyl acetylenedicarboxylate to the β-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.
