Front Cover: BF₄⁻ as source for the preparation of BF₂ bridged copper(II) dimethylglyoxime complexes (Z. Anorg. Allg. Chem. 16/2022)

Abstract

The cover picture shows a closer look at the decomposition of the tetrafluoroborate anion (BF4‐) during the reaction of Cu(BF4)2⋅6H2O and dimethylglyoxime (H2dmg) to formally “BF2+” and 2F‐. Whereas the high affinity of fluoride anions towards silicon lead to the formation of SiF62‐, BF2 is inserted into the ligand framework to yield diverse O,O‐bidentate difluoroboron copper(II) complexes. These resulting complexes have been isolated and structurally characterized. Their molecular structures frame the magnifying glass that highlights the decomposition of BF4‐. (DOI: 10.1002/zaac.202200150).

Cooperativity‐Driven Reactivity of a Dinuclear Copper Dimethylglyoxime Complex

“…At 435 nm (ɛ m = 2471 L mol À 1 cm À 1 ) a weaker absorption maximum is visible, which previously was assigned to transitions into LMCT (ligand-to-metal-charge-transfer) states. [12][13][14] The experimental spectrum is in excellent agreement with the time-dependent (TD) DFT predicted UV/Vis-spectrum that predicted two maxima at 230 and 270 nm and several maxima of lower intensity at higher wavelengths (see the Supporting Information Sections 2, 9.3, and 9.6, Figures S49, S51-S56, and Table S15). The spectroscopic signature of 2 resembles that of 1, where the main difference is the inversed intensity ratio of the bands at 228 and 275 nm, (ɛ m = 14 474 L mol À 1 cm À 1 and ɛ m = 9244 L mol À 1 cm À 1 , respectively) caused by the different coordination modes of the ligands.…”

“…determined for both compounds (Figure 1) and resemble comparable structures described in the literature. [10,[12][13][14]23] Additionally, structure optimization was performed at B3LYP/def2-TZVP level, which showed good geometrical agreement with the experimental results (Figure S47, Table S26 in the Supporting Information). The structure of 2 resembles that known for nickel(II) ions.…”

“…[9] Copper(II) dimethylglyoxime (H 2 dmg) complexes are suitable for the investigation of such a cooperative effect because a variety of complexes differing in their composition are known. These complexes include mono-, [10][11][12] di- [12][13][14][15] and tetranuclear [15,16] complexes, which have been characterized by crystal structure analysis, [10][11][12][13][14][15][16] IR spectroscopy, [11][12][13]16,17] UV/Vis spectroscopy, [12][13][14]16,18] EPR [19] and other magnetic methods. [13,14,16] Additionally, mixtures of Cu II salts and dimethylglyoxime have been applied in catalytic reactions such as the N-arylation of imidazole derivatives [20] and the decomposition of hydrogen peroxide with subsequent oxidation of benzyl alcohol and ethylbenzene (zeolite encapsulated).…”

“…[13,14,16] Additionally, mixtures of Cu II salts and dimethylglyoxime have been applied in catalytic reactions such as the N-arylation of imidazole derivatives [20] and the decomposition of hydrogen peroxide with subsequent oxidation of benzyl alcohol and ethylbenzene (zeolite encapsulated). [21] Due to our interest in multinuclear copper complexes and their reactivity, [12,22] we focused on the dinuclear complex [Cu 2 (H 2 dmg)(Hdmg)(dmg)] + (1) and its mononuclear analogue [Cu(Hdmg) 2 ] (2) as comparison (Figure 1). Two of the possible three isomers of 1 have been reported, whereas isomer I is predominant in literature [13,14,16] and favored with increasing pH value.…”

“…Due to our interest in multinuclear copper complexes and their reactivity, [12,22] we focused on the dinuclear complex [Cu 2 (H 2 dmg)(Hdmg)(dmg)] + ( 1 ) and its mononuclear analogue [Cu(Hdmg) 2 ] ( 2 ) as comparison (Figure 1). Two of the possible three isomers of 1 have been reported, whereas isomer I is predominant in literature [13,14,16] and favored with increasing pH value [13] .…”