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Keywords:

  • Methylamine;
  • Manganese;
  • Homoleptic complex;
  • Solvothermal synthesis;
  • Pentaselenide

Abstract

[Mn(NH2CH3)6]Cl2 (1) and [Mn(NH2CH3)6]Se5 (2) were prepared by solvothermal reactions in liquid methylamine from MnCl2 at 150 °C for 1 and from a mixture of MnCl2, Rb2Se and selenium at 120 °C for 2. Both 1 and 2 were obtained in high yields as colorless and dark-red crystals and represent the first homoleptic methylamine complexes with coordination number six. Compound 1 crystallizes rhombohedral (Requation image, Z = 3) and is built of only slightly distorted octahedral [Mn(NH2CH3)6]2+ cations and Cl anions. Compound 2 crystallizes orthorhombic (Pnna, Z = 4) and is built of octahedral [Mn(NH2CH3)6]2+ cations showing a strong angular distortion and of Se52– anions in the form of chains in transoid conformation. DFT calculations reveal an almost undistorted ground state structure for [Mn(NH2CH3)6]2+ with N–Mn–N angular distortions of 1° from orthogonality, close to the structure found for the complex in 1. The calculated energy necessary for a distortion as found in the structure of 2 is rather low and amounts to 26 kJmol–1 which is in the range typical for hydrogen bonds. The N–Mn–N angular distortions of the complex cation in 2, observed in the range of 10°, is caused by cation-anion interactions in the crystal structure by N–H····Se hydrogen bonds.