Steric and electronic factor comparisons in hydrotris(3-phenylpyrazolyl)borate nickel(II) aryloxides.
Hydrotris(pyrazolyl)borate (Tp) ligands, also known as scorpionates, are potent tridentate donors that effectively bind metal ions in a face-capping array. Hydrotris(3-phenylpyrazolyl)borate enforces a tetrahedral environment on NiIIto model metalloenzymes. The syntheses and structural characterizations of a number of [hydrotris(3-phenylpyrazolyl)borato]nickel(II) aryloxides were performed to provide insight into the environment of the model active site; these compounds are chlorido[hydrotris(3-phenylpyrazolyl-κN2)borato](3-phenyl-1H-pyrazole-κN2)nickel(II) chloroform monosolvate, [Ni(C27H22BN6)Cl(C9H8N2)]·CHCl3, (2), [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)nickel(II), [Ni(C27H22BN6)(C6H5O)], (3), (2,6-dimethylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II) [Ni(C27H22BN6)(C8H9O)], (4), (4-tert-butylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II), [Ni(C27H22BN6)(C10H13O)], (5), and [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)(tetrahydrofuran-κO)nickel(II) tetrahydrofuran monosolvate, [Ni(C27H22BN6)(C6H5O)(C4H8O)]·C4H8O, (6). Alkyl groups, e.g. tert-butyl in (5) and methyl in (4), electronically activate the aryloxide group to intramolecular π-π stacking but can be frustrated by steric encumbrance at the interacting ring faces. The flexibility at the nickel coordination site, afforded by the uncrowded B atom of the TpPhligand, allows tetrahydrofuran coordination in the phenolate compound.
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
William L
WL
Green
Sabine River Laboratory B568, INVISTA, Orange, TX 77631, USA.
Eric R
ER
Sirianni
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
Glenn P A
GP
Yap
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
Charles G
CG
Riordan
aryloxide; crystal structure; nickel; scorpionates; steric; tris(pyrazolyl)borate; π–π stacking