Synthesis and Reactions of 3d Metal Complexes with
the Bulky Alkoxide Ligand [OC<sup><i>t</i></sup>Bu<sub>2</sub>Ph]
- Publication date
- Publisher
Abstract
Treatment
of NiCl<sub>2</sub>(dme) and NiBr<sub>2</sub>(dme) (dme = dimethoxyethane)
with 2 equiv of LiOR (OR = OC<sup><i>t</i></sup>Bu<sub>2</sub>Ph) forms the distorted trigonal planar complexes [NiLiX(OR)<sub>2</sub>(THF)<sub>2</sub>] (THF = tetrahydrofuran) <b>5</b> (X
= Cl) and <b>6</b> (X = Br). The reaction of CuX<sub>2</sub> (X = Cl, Br) with 2 equiv of LiOR affords the Cu(I) product Cu<sub>4</sub>(OR)<sub>4</sub> (<b>7</b>). The same product can be
obtained using the Cu(I) starting material CuCl. NMR studies indicated
that the reduction of Cu(II) to Cu(I) is accompanied by the oxidation
of the alkoxide RO<sup>–</sup> to form the alkoxy radical RO<sup>•</sup>, which subsequently forms <i>tert</i>-butyl
phenyl ketone by β-scission. Treatment of compounds <b>1</b>–<b>4</b> ([M<sub>2</sub>Li<sub>2</sub>Cl<sub>2</sub>(OR)<sub>4</sub>], M = Cr–Co) with thallium hexafluorophosphate
allowed the isolation of the distorted tetrahedral complexes of the
form M(OR)<sub>2</sub>(THF)<sub>2</sub> for M = Mn (<b>8</b>), Fe (<b>9</b>), and Co (<b>10</b>). Cyclic voltammetry
performed on compounds <b>8</b>–<b>10</b> demonstrated
irreversible oxidations for all complexes, with the iron complex <b>9</b> being the most reducing. Complex <b>9</b> shows a
reactivity toward PhIO and Ph<sub>3</sub>SbS to form the corresponding
dinuclear iron(III) complexes Fe<sub>2</sub>(O)(OR)<sub>4</sub>(THF)<sub>2</sub> (<b>11</b>) and Fe<sub>2</sub>(S)(OR)<sub>4</sub>(THF)<sub>2</sub> (<b>12</b>), respectively. X-ray structural
studies were performed, showing that the Fe–O–Fe angle
for complex <b>11</b> is 176.4(1)° and that the Fe–S–Fe
angle for complex <b>12</b> is 164.83(3)°
