Rhenium bound methyl

The first step in a one-pot formation of a phenanthrene ring system from an enantiomericaUy pure rhenium-bound naphthalene is a TBDMS triflate-promoted Michael addition to 3-penten-2-one (eq 26). Electron-rich rhenium-bound naphthalenes also undergo TBDMS triflate-promoted conjugate addition reactions to less-activated Michael acceptors such as methyl acrylate, leading to the formal Diels-Alder cycloaddition product of naphthalene with this dienophile. ... 

Perhaps the strongest evidence for the formation of an alkane complex comes from the low temperature NMR experiments with CpRe(CO)3. Irradiation at —80°C in cyclopentane results in the formation of CpRe(CO)2(c-pentane), for which a resonance for theCH2 bound to the metal is observed in the NMR spectrum at 5 —2.32, consistent with either a symmetrical binding of both hydrogens ( 7 -H,H) or a rapid interchange between two cr-C-H ( -C,H) complexes. Irradiation in pentane solvent leads to the formation of three distinct species, assigned as coordination of rhenium to the methyl, Q-methylene, and central methylene of pentane (Equation (7)). ... 

The excited state quenching reactions of this rhenium carbonyl system can be studied by replacing the spectator chloride ligand with one that can itself act as an intramolecular quencher. One such complex is Re(CO)3(bpy)(py-PTZ), where py-PTZ is a phenothiazine (Fig. 6.3). Another such complex is Re(CO)3(bpy)(MQ" ), where MQ" is the -methyl-4,4 -bipyridinium cation (Fig. 6.4). ° ° In each case the initial MLCT (Re bpy) excited state undergoes intramolecular electron transfer to the chemically bound quencher ... 

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