Anodic Preparation of [Re₂Cp₂(CO)₆]²⁺:  A Dimeric Dication that Provides the Powerful One-Electron Oxidant [ReCp(CO)₃]⁺

Abstract

The half-sandwich piano-stool compounds Re(eta5-C5R5)(CO)3 (1, R = H; or 2, R = Me) are oxidized to the corresponding 17-electron Re(II) cations at glassy carbon anodes in CH2Cl2/[NBu4][B(C6F5)4]. Despite the very strongly positive E1/2 values of the couples (1.16 V for 1/1+ and 0.91 V for 2/2+ vs ferrocene/ferrocenium), the radical cations are persistent in this medium and exist in equilibrium with the corresponding dimeric dications, which may be cathodically reduced back to the neutral starting material. DFT calculations show that the dimer of 1+ achieves its stability through formation of a single long (almost 3.3 A) Re-Re bond made possible when the HOMO in 1 is rehybridized away from the metal in the one-electron oxidation process. The pure salts [1][B(C6F5)4]2 and [2][B(C6F5)4]2 were isolated by preparative anodic electrochemistry. The former may be used for storage of the very strong one-electron oxidant 1+, which was used to prepare a number of oxidation products as their [B(C6F5)4]- salts.

Organometallic diphenols: The importance of the organometallic moiety on the expression of a cytotoxic effect on breast cancer cells

“…The diversity of their electrochemical behavior, however, makes it impossible to offer any correlation, except to remark that only in the case of the ferrocene compounds did the electrochemical behavior suggest QM formation. The radical cations of 10-12 are extremely unstable; indeed, the efforts to generate stable 17-electron ruthenium and [CpM(CO) 3 ] + species have been considerable, and have only recently been successful by the use of weakly coordinating anion electrolytes [16,20]. On the other hand, although compound 7 did give rise to a reversible one electron metal centered redox couple, it did not display any intramolecular electron transfer behavior, and showed no reactivity with pyridine what- soever.…”

Organometallic Electrochemistry: Origins, Development, and Future

“…Taking advantage of this change in supporting electrolytes, new chemistry has been described for the cation radicals of ruthenocene, 17 CoCp(CO) 2 , 220,221 Cr-(benzene)(CO) 3 , 220 and ReCp(CO) 3 . 222 In addition, an integrated (solvent/electrolyte) approach to medium effects has been introduced. 223 (9) Methodology: The Contemporary Experimental Approach.…”

Asymmetric Synthesis, Characterization and Stereoselectivity of Novel 1-{2-[(1R,2S)-2-(Chloromethyl)cyclopropyl]ethyl}-4-methoxybenzene via Boronate Complex

“…Gauthier et al 1 converted boronic esters into reactive nucleophiles and resulting boronate complexes were reacted with a number of electrophiles with inversion of stereochemistry. Lou et al 6 , Chong et al 7 and Goodman and Pellegrinet 8 synthesized reactive boronate species by replacing alkoxy groups with biphenols. Vedejs et al 9 converted many amino acids into asymmetric boronate complexes.…”

“…) Carbamate (4) was characterized through 1 H NMR, 13 C NMR and functional groups were confirmed through IR. This crude product (4) was used for the synthesis of (R)-2-(1-(4methoxyphenyl)hex-5-en-3-yl)-4,4,5,5-tetramethyl-1,3,2dioxaborolane (6) and 2-(1-(4-methoxyphenyl)hex-5-en-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7). (1.88 mL, 8.18 mmol, 1.2 eq.)…”

“…(3) (4) Synthesis of 2-(1-(4-methoxyphenyl)hex-5-en-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7): Racemic 2-(1-(4-methoxyphenyl)hex-5-en-3-yl)-4,4,5,5-tetramethyl-1,3,2dioxaborolane (7) was prepared by substituting (-)sparteine by N,N,N,N-tetramethylethylenediamine (TMEDA) (1.22 mL, 8.18 mmol, 1.2 eq.) (5b) (Fig.…”