Selective Synthesis of a New Macropolycycle Containing One N-CH2-N Linkage and Its Reaction with Cu2+ and Ni2+ Ions in Methanol

The reaction of 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.0$0^{1.18}.0^{7.12}$]docosane ($L^1$) with formaldehyde in warm methanol yielded 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.$1^{2.6}.0^{1.18}.0^{7.12}$]tricosane ($L^7$) containing one 1,3-diazacyclohexane subunit. In methanol, $L^7$ readily reacts with $Cu^{2+}$ ion to form [$CuL^7(H_2O)$]$^{2+}$ which is extremely inert against methanolysis. In the solution containing $Ni^{2+}$ ion, however, $L^7$ reacts with methanol to yield [$NiL^3$]$^{2+}$ ($L^3$ = 2-(methoxymethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.$0^{1.18}.0^{7.12}$]- docosane), in which one N-$CH_2OCH_3$ pendant arm is appended. The copper(II) complex [$CuL^7(H_2O)$]- $(ClO_4)_2{\cdot}3H_2O\;(I{\cdot}3H_2O)$ has a severely distorted trigonal bipyramidal coordination geometry with a 4-5- 6-5 chelate ring sequence. The crystal structure of [$NiL^3$]$(PF_6)_2{\cdot}2H_2O$ (IIb) shows that the N-$CH_2OCH_3$ pendant arm is not coordinated to the metal ion in the solid state. In various solvents (S), however, the nickel(II) complex exists as a mixture of [$NiL^3$(S)]$^{2+}$, in which the N-$CH_2OCH_3$ group as well as S is coordinated to the metal ion, and [$NiL^3$]^{2+}.