Hydroamination of alkenes or alkynes is one of the most straightforward methods to form C-N bonds and nitrogen-containing heterocycles. A simple Lewis acid Al(OTf) was found to be an effective precatalyst for the hydroamination of unactivated primary and secondary alkenylamines between 110 and 150 °C. Subsequent studies show that other metal triflates are also effective precatalysts for the hydroamination reactions. For metal triflate salts, mechanistic studies, including kinetics, are consistent with the in situ generation of triflic acid, which likely serves as the active catalyst.
Ligands containing linked dipicolylamine (dpa) and bipyridine (bpy) sites have been utilized in the synthesis of monometallic and heterometallic complexes. The two sites have different selectivities for metal binding, which allows preferential formation of singly metalated complexes. The dpa site of the ligands has been observed to bind selectively to Zn(2+), Pd(2+), and Pt(2+), while the bpy site binds selectively to Rh(+). Addition of a second metal then results in the formation of heterometallic products. In the presence of CD3OD, the heterometallic Rh/Pt and Rh/Pd complexes undergo rapid selective H/D exchange of one of the diastereotopic protons of the dpa methylene group.
A protocol is presented for the synthesis of chromium(III) complexes of the type cis-[Cr(diimine)2(1-methylimidazole)2](3+). These compounds exhibit large excited-state oxidizing powers and strong luminescence in solution. Emission is quenched by added guanine, yielding rate constants that track the driving force for guanine oxidation. The cis-[Cr(TMP)(DPPZ)(1-MeImid)2](3+) species binds strongly to duplex DNA with a preference for AT base sites in the minor groove and may serve as a precursor for photoactivated DNA covalent adduct formation.
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