| Popis: |
Addition of two equivalents of benzyl bromide to [N,N′-bis(2-mercaptoethyl)-1,5-diazacyclooctane]nickel(II) (Ni-1) produced the green dibenzyl dithioether complex [Ni-1-Bzl2Br2] structurally characterized by X-ray crystallography as a six-coordinate octahedral complex in a monoclinic crystal system and the P21/c space group. Benzylation of the methyl thioether/thiolate [(Ni-1-Me)+I– yielded the mixed benzyl/methyl dithioether [(Ni-1-BzlMe)Br]I, structurally characterized by X-ray crystallography as a five-coordinate square pyramidal nickel(II) complex with a Ni–Br distance of 2.451 A. The complex crystallizes in the orthorhombic Cmca space group. The latter is the first nickel(II) pentacoordinate complex isolated for the N,N′-bis(2-mercaptoethyl)-1,5-diazacyclooctane (daco) ligand. Structural comparison of these two complexes with the square-planar dimethyl compound [Ni-1-Me2]I2 found an expansion of the N2S2 plane upon addition of axial ligands. The five-coordinate nickel complex showed a displacement of the Ni ion from the N2S2 plane by 0.43 A toward the axial bromide ligand, a common observation of pentacoordinate complexes of this ligand with metals such as Zn and Fe. Electrochemical studies as well as the X-ray crystal structures for complex [Ni-1-Bzl2Br2] and [(Ni-1-BzlMe)Br]I are presented and discussed in detail. |
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