Copper Catalysed Oxygenation of Bis (2-pyridyl) methane and 6-Methyl-bis (2-pyridyl)methane to the Corresponding Ketones

The ligands (L) bis (2-pyridyl) methane (BPM) and 6-methyl-bis (2-pyridyl)methane (MBPM) form the three complexes CuL2+, CuL, and Cu2L2H with Cu2+. Stability constants are log K1 = 6.23 ± 0.06, log K2 = 4.83 ± 0.01, and log K (Cu2L2H + 2H2+ ⇌ 2 CuL2+) = −10.99 ± 0.03 for BPM and 4.56 ± 0.02, 2.64 ± 0.02, and −11.17 ± 0.03 for MBPM, respectively. In the presence of catalytic amounts of Cu2+, the ligands are oxygenated to the corresponding ketones at room temperature and neutral pH. With BPM and 2,4,6-trimethylpyridine (TMP) as the substrate and the buffer base, respectively, the kinetics of the oxygenation can be described by the rate law with k1 = (5.9 ± 0.2) · 10−13 mol l−1 s−1, k2 = (4.0 ± 0.6) · 10−4 mol−1 ls−1, k3 = (1.1 ± 0.1) · 10−12 mol l−1 s−1, and k4 = (9 ± 2) · 10−14 mol l−1 s−1.