The methylcobalt(III) complex of a tetrapodal pentadentate amine ligand, 2,6-bis(1′,3′-diamino-2′-methyl-prop-2′-yl)pyridine

The pentaamine methylcobalt(III) compound [Co(pyN4)(CH3)](NO3)2 (pyN4=2,6-bis(1′,3′-diamino-2′-methyl-prop-2′-yl)pyridine) has been synthesised from [Co(NH3)5(CH3)](NO3)2 and pyN4 by ligand exchange, and characterised by IR, 1H, 13C and 59Co NMR spectroscopy as well as elemental analysis. The structure of the complex has been determined using the dithionate salt [Co(pyN4)(CH3)]S2O6. The coordination geometry at cobalt is close to octahedral, the tetrapodal pentadentate amine ligand providing a C2-symmetrical coordination cap for the metal centre. One axial position is occupied by the pyridine nitrogen atom, while the four equivalent primary amino groups take the equatorial positions. The other axial position, trans to the pyridine ring, is occupied by the methyl group. The Co–Npy bond length of 2.018(2) Å is significantly elongated compared with other cobalt(III) complexes of the pyN4 ligand, demonstrating the strong trans influence of the CH3 ligand. The Co–C bond length (1.975(4) Å) is virtually identical to the value found in the related complex [Co(NH3)5(CH3)](S2O6).