Synthesis and characterisation of manganese(II) compounds with tetradentate ligands based on the bispidine backbone

Reaction of the tetradentate ligand dimethyl 3,7-dimethyl-9-oxo-2,4-bis(2-p yridyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate (L-1) with manganes e(II) chloride or iodide in methanol yielded [(MnLCl2)-Cl-1] and [(MnLI2)-I -1], respectively. Reaction with silver(I) triflate Ag(O3SCF3) converted th ese compounds into [MnL1(O(3)SCF3)(2)]. Reduction of L-1 with NaBH4 in MeOH and LiAlH4 in THF led to the triol I, 5-bis(hydroxymethylene)-3,7-dimethyl -2,4-bis(2-pyridyl)-3,7-diazabicyclo[3.3.1]nonan-9-ol (L-2); the reduction is stereoselective and yields the syn isomer. Complexation of manganese(Ii) chloride and iodide with L-2 produced [(MnLCl2)-Cl-2] and [(MnLI2)-I-2] an d these have a higher thermal stability than [(MnLX2)-X-1]. The complexes [ (MnLCl2)-Cl-1], [(MnLI2)-I-1], [MnL1(O3SCF3)(2)], [(MnLCl2)-Cl-2] and [(MnL I2)-I-2] are characterised spectroscopically, electrochemically and by thei r magnetic, conductometric, thermal and structural properties (X-ray analys es of [(MnLCl2)-Cl-1] and [(MnLCl2)-Cl-2]).