Reductive Coupling of Azides Mediated by an Iron(II) Bis(alkoxide) Complex

The iron­(III) hexazene complex (RO)₂Fe­(μ-κ²:κ²-AdN₆Ad)­Fe­(OR)₂ (<b>3</b>) was synthesized via reductive coupling of 1-azidoadamantane at the iron­(II) bis­(alkoxide) complex Fe­(OR)₂(THF)₂ (<b>2</b>). The X-ray crystal structure depicts electron delocalization within the hexazene moiety. Density functional theory studies propose the formation of an iron azide dimer on the route to hexazene, in which each azide is monoreduced and the iron centers are oxidized to the 3+ oxidation state

Reductive Coupling of Azides Mediated by an Iron(II) Bis(alkoxide) Complex

The iron­(III) hexazene complex (RO)₂Fe­(μ-κ²:κ²-AdN₆Ad)­Fe­(OR)₂ (<b>3</b>) was synthesized via reductive coupling of 1-azidoadamantane at the iron­(II) bis­(alkoxide) complex Fe­(OR)₂(THF)₂ (<b>2</b>). The X-ray crystal structure depicts electron delocalization within the hexazene moiety. Density functional theory studies propose the formation of an iron azide dimer on the route to hexazene, in which each azide is monoreduced and the iron centers are oxidized to the 3+ oxidation state

Reactivity Modes of an Iron Bis(alkoxide) Complex with Aryl Azides: Catalytic Nitrene Coupling vs Formation of Iron(III) Imido Dimers

The iron bis­(alkoxide) complex Fe­(OR)₂(THF)₂ (R = C^tBu₂Ph), <b>1</b>, was found to have strikingly different reactivity with various aryl azides, ArN₃. Azides with methyl or ethyl groups in the <i>ortho</i> positions of the phenyl ring react catalytically via nitrene coupling to give azoarenes, ArNNAr. Catalyst loading as low as 1 mol % yields clean, quantitative conversion of aryl azides to azoarenes at room temperature in as little as 4 h. A combination of two different aryl azides leads to the catalytic formation of all three possible azoarenes, including the asymmetric one. In contrast, reactions with aryl azides lacking <i>ortho</i> substituents yield stable dimeric iron imido complexes of the form (RO)­(THF)­Fe­(μ-NAr)₂­Fe­(THF)­(OR) (Ar = 4-(trifluoromethyl)­phenyl, <b>5</b>; Ar = phenyl, <b>6</b>; Ar = 3,5-dimethylphenyl, <b>7</b>), which do not undergo catalytic nitrene coupling. The isocyanide adduct Fe­(OR)₂(CNR)₂ (<b>4</b>, R = 2,6-dimethylphenyl) was obtained from the reaction of Fe­(OR)₂(THF)₂ with two equivalents of isocyanide. No C–N bond formation was observed in the reaction of compound <b>4</b> with azides or in the reaction of compounds <b>5</b>–<b>7</b> with isocyanides

Synthesis and Characterization of a Stable High-Valent Cobalt Carbene Complex

The formally Co^IV carbene Co­(OR)₂(CPh₂) is formed upon the reaction of diphenyl­diazo­methane with the cobalt bis­(alkoxide) precursor Co­(OR)₂(THF)₂. Structural, spectroscopic, and theoretical studies demonstrate that Co­(OR)₂(CPh₂) has significant high-valent Co^IVCPh₂ character with non-negligible spin density on the carbene moiety

Synthesis and Characterization of a Stable High-Valent Cobalt Carbene Complex

The formally Co^IV carbene Co­(OR)₂(CPh₂) is formed upon the reaction of diphenyl­diazo­methane with the cobalt bis­(alkoxide) precursor Co­(OR)₂(THF)₂. Structural, spectroscopic, and theoretical studies demonstrate that Co­(OR)₂(CPh₂) has significant high-valent Co^IVCPh₂ character with non-negligible spin density on the carbene moiety

Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

The atomic layer deposition (ALD) of films with the approximate compositions Mn3(BO3)2 and CoB2O4 is described using MnTp2 or CoTp2 [Tp ¼ tris(pyrazolyl)borate] with ozone. The solid state decomposition temperatures of MnTp2 and CoTp2 are 370 and 340 C, respectively. Preparative-scale sublimations of MnTp2 and CoTp2 at 210 C/0.05 Torr afforded >99% recoveries with <0.1% nonvolatile residues. Self-limited ALD growth was demonstrated at 325 C for MnTp2 or CoTp2 with ozone as the coreactant. The growth rate for the manganese borate process was 0.19 A˚ /cycle within the ALD window of 300–350 C. The growth rate for the cobalt borate process was 0.39–0.42 A˚ /cycle at 325 C. X-ray diffraction of the as-deposited films indicated that they were amorphous. Atomic force microscopy of 35–36 nm thick manganese borate films grown within the 300–350 C ALD window showed root mean square surface roughnesses of 0.4–0.6 nm. Film stoichiometries were assessed by x-ray photoelectron spectroscopy and time of flight-elastic recoil detection analysis. The differing film stoichiometries obtained from the very similar precursors MnTp2 and CoTp2 are proposed to arise from the oxidizing ability of the intermediate high valent manganese oxide layers and lack thereof for cobalt.peerReviewe

Synthesis and Reactions of 3d Metal Complexes with the Bulky Alkoxide Ligand [OC^<i>t</i>Bu₂Ph]

Treatment of NiCl₂(dme) and NiBr₂(dme) (dme = dimethoxyethane) with 2 equiv of LiOR (OR = OC^<i>t</i>Bu₂Ph) forms the distorted trigonal planar complexes [NiLiX­(OR)₂(THF)₂] (THF = tetrahydrofuran) <b>5</b> (X = Cl) and <b>6</b> (X = Br). The reaction of CuX₂ (X = Cl, Br) with 2 equiv of LiOR affords the Cu­(I) product Cu₄(OR)₄ (<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^– to form the alkoxy radical RO^•, which subsequently forms <i>tert</i>-butyl phenyl ketone by β-scission. Treatment of compounds <b>1</b>–<b>4</b> ([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 (<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 Ph₃SbS to form the corresponding dinuclear iron­(III) complexes Fe₂(O)­(OR)₄(THF)₂ (<b>11</b>) and Fe₂(S)­(OR)₄(THF)₂ (<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)°