Terminal NiII−OH/−OH2 complexes in trigonal bipyramidal geometries derived from H2O. (29th March 2017)

• Record Type: Journal Article
• Authors: Lau, Nathanael; Sano, Yohei; Ziller, Joseph W.; Borovik, A.S.
• Is Part Of: Polyhedron. Volume 125(2017)
• Page Start: 179
• Page End: 185
• Publication Date: 2017-03-29
• Subjects: Nickel-hydroxido complexes -- Nickel-aqua complexes -- Tripodal ligands -- Hydrogen bonds -- Nickel(III) complexes; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2016.11.015
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: A terminal Ni II –OH complex and a terminal Ni II –OH2 complex, both supported by tripodal ligands, have been prepared and characterized. The solid state structures of these complexes reveal that they adopt distorted trigonal bipyramidal primary coordination spheres, an unusual geometry for Ni II complexes. Treating these complexes with one-electron oxidants formed species with S = 1/2 spin ground states, which are consistent with formation of monomeric Ni III species. Abstract: The preparation and characterization of two Ni II complexes are described, a terminal Ni II –OH complex with the tripodal ligand tris[(N)- tert -butylureaylato)-N-ethyl)]aminato ([H3 buea] 3− ) and a terminal Ni II –OH2 complex with the tripodal ligand N, N′, N″ -[2, 2′, 2″-nitrilotris(ethane-2, 1-diyl)]tris(2, 4, 6-trimethylbenzenesulfonamido) ([MST] 3− ). For both complexes, the source of the –OH and –OH2 ligand is water. The salts K2 [Ni II H3 buea(OH)] and NMe4 [Ni II MST(OH2 )] were characterized using perpendicular-mode X-band electronic paramagnetic resonance, Fourier transform infrared, UV–vis spectroscopies, and its electrochemical properties were evaluated using cyclic voltammetry. The solid state structures of these complexes determined by X-ray diffraction methods reveal that they adopt a distorted trigonal bipyramidal geometry, an unusual structure for 5-coordinate Ni II complexes. Moreover, the Ni II –OH and Ni II –OH2 units form intramolecular hydrogen bonding networks with the [H3 buea] 3− and [MST] 3− ligands. The oxidation chemistry of these complexes was explored by treating the high-spin Ni II compounds with one-electron oxidants. Species were formed with S = 1/2 spin ground states that are consistent with formation of monomeric Ni III species. While the formation of Ni III –OH complexes cannot be ruled out, the lack of observable O–H vibrations from the putative Ni–OH units suggest the possibility that other high valent Ni species are formed.