Synthesis and Reactions of 3d Metal Complexes with the Bulky Alkoxide Ligand [OC t Bu2Ph]

Treatment of NiCl2(dme) and NiBr2(dme) (dme = dimethoxyethane) with 2 equiv of LiOR (OR = OC t Bu2Ph) forms the distorted trigonal planar complexes [NiLiX­(OR)2(THF)2] (THF = tetrahydrofuran) 5 (X = Cl) and 6 (X = Br). The reaction of CuX2 (X = Cl, Br) with 2 equiv of LiOR affords the Cu­(I) product Cu4(OR)4 (7). 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– to form the alkoxy radical RO•, which subsequently forms tert-butyl phenyl ketone by β-scission. Treatment of compounds 1–4 ([M2Li2Cl2(OR)4], M = Cr–Co) with thallium hexafluorophosphate allowed the isolation of the distorted tetrahedral complexes of the form M­(OR)2(THF)2 for M = Mn (8), Fe (9), and Co (10). Cyclic voltammetry performed on compounds 8–10 demonstrated irreversible oxidations for all complexes, with the iron complex 9 being the most reducing. Complex 9 shows a reactivity toward PhIO and Ph3SbS to form the corresponding dinuclear iron­(III) complexes Fe2(O)­(OR)4(THF)2 (11) and Fe2(S)­(OR)4(THF)2 (12), respectively. X-ray structural studies were performed, showing that the Fe–O–Fe angle for complex 11 is 176.4(1)° and that the Fe–S–Fe angle for complex 12 is 164.83(3)°.