Synthesis and Reactions of 3d Metal Complexes with the Bulky Alkoxide Ligand [OC^tBu₂Ph]

Abstract

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)°.

Zinc bimetallics supported by a xanthene-bridged dinucleating ligand: synthesis, characterization, and lactide polymerization studies

“…In contrast, in the corresponding nickel(II) structure (Ni(OR)(m 2 -Cl)(m 2 -OR)Li(THF) 2 ), the chloride was bridging while one of the alkoxides was terminal. 24 The bridging nature of both alkoxides in Zn(Cl)(m 2 -OR) 2 Li(THF) supports the notion of the increased alkoxide basicity when coordinated to zinc.…”

“…We note that while this behaviour stands in contrast to the Cr(II), Mn(II), Fe(II), and Co(II), for which M(OR) 2 (THF) 2 could be isolated in good yields following similar protocols, 24,22a Ni(II) and Cu(II) also failed to lead to isolable M(OR) 2 (THF) 2 complexes. 24 As we could not isolate pure "Zn(OR) 2 ", we investigated the reactivity of L with two equivalents of complex 1, or with "Zn(OR) 2 " prepared in situ. Slow addition of L to the cold (À35 C) THF solution containing two equivalents of complex 1 led to the clean formation of mononuclear complex 2 (Scheme 1).…”

Catalytic synthesis of azoarenes via metal-mediated nitrene coupling

“…65 Furthermore, π donation from an alkoxide ligand can compete with the π-donation from the imido group, decreasing the multiple MvNR bond character and increasing its group transfer reactivity. Groysman, Lord, and coworkers have synthesized series of well-defined Cr(II)-Co(II) transition metal complexes with bulky alkoxide ligand OR (OR = OC t Bu 2 Ph), 66,67 and explored their reactivity in group-transfer reactions. 37,68 Mononuclear M(OR) 2 (THF) 2 precursors (M = Mn, Fe, Co) complexes exhibited geometry intermediate between tetrahedral and seesaw, featuring wide interalkoxide angle (130-139°), and narrow angle between THF ligands (83-88°).…”

“…37,68 Mononuclear M(OR) 2 (THF) 2 precursors (M = Mn, Fe, Co) complexes exhibited geometry intermediate between tetrahedral and seesaw, featuring wide interalkoxide angle (130-139°), and narrow angle between THF ligands (83-88°). 67 The steric bulk of the alkoxides, manifesting itself in the seesaw distortion, enables formation of the reactive trigonal planar intermediates upon treatment with a group-transfer reagent. [69][70][71] The iron(II) complex Fe(OR) 2 (THF) 2 was found to exhibit reactivity in azoarene formation.…”

Tetrakis[μ2-1,1,1,3,3,3-hexafluoro-2-(trifluoromethyl)propan-2-olato]tetrakis(μ3-2-methylpropan-2-olato)octacopper(I)

“…Of particular interest are the alkoxide complexes of copper(I), which often form cluster compounds (Purdy & George 1995;Borup et al, 1997;Purdy & George 1998;Anson et al, 2005;Lieberman et al, 2015). Within this set of compounds, there are those that form tetra-Cu I squares bridged along the edges by oxygen donors (Greiser & Weiss, 1976;McGeary et al, 1992;Terry et al, 1996;Lopes et al, 1997;Nikitinsky et al, 2000;Hå kansson et al, 2000;Krossing, 2012;Bellow et al, 2015). In view of the interesting chemistry exhibited by these alkoxide complexes containing Cu I , the synthesis of a mixed alkoxide complex was attempted and resulting structure of the compound is reported.…”