Structural and Electrochemical Comparison of NiII in an N2S2 Plane with Two, One and No Axial Ligands: Isolation and Characterization of a Five-Coordinate Nickel(II) Complex
✍ Scribed by Buonomo, Rizalia M. ;Reibenspies, Joseph H. ;Darensbourg, Marcetta Y.
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1996
- Tongue
- English
- Weight
- 602 KB
- Volume
- 129
- Category
- Article
- ISSN
- 0009-2940
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✦ Synopsis
Addition of two equivalents of benzyl bromide to [N,N'-bis(2-mercaptoethy1)-1,5-diazacyclooctane]nickel(II) (Ni-1) produced the green dibenzyl dithioether complex [Ni-l-BzlzBrz] structurally characterized by X-ray crystallography as a sixcoordinate octahedral complex in a monoclinic crystal system and the P21/c space group. Benzylation of the methyl thioether/thiolate [(Ni-l-Me)+Iyielded the mixed benzyVmethy1 dithioether [(Ni-1-BzlMe)Br]I, structurally characterized by X-ray crystallography as a five-coordinate square pyrFmidal nickel(I1) 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(I1) pentacoordinate complex iso-
The complex [N;N'-bis(2-mercaptoethyl)-l,5-diazacyclooctane]nickel(Il) (Ni-1) reacts with methyl iodide sequentially to produce monomethylated['] and dimethyl-atedL21 derivatives. In both cases, the nickel product is fourcoordinate square planar with the iodides present as noninteracting counterions. Reaction of Ni-1 with 1,3-dibromopropane forms the 14-membered macrocycle Ni-lmicycle)BrZ in which one of the bromides is 2.947(2) A from the nickel Although this is ca. 0.5 A beyond the Ni-Br bonding distance (average 2.41 the bromide's position as a long range axial ligand in a square pyramid is inferred by the Br-Ni-S and the Br-Ni-N angles of approximately 88 and 98 ' , respe~tively[~I. Further, the NiIUr redox potential of -0.71 V (referenced to NHE in CH3CN) is some 0.3 V less accessible than [Ni-l(bicycle)][BPh4jz, suggesting that the Br---Ni" interaction is retained in solution and destabilizes Ni'.
Ni-l(bicycle)Br,