Reversible Oxidative Se−Se Coupling of Phosphine Selenides by Ph₃Sb(OTf)₂

Abstract

The coordination chemistry of p-blockc enters as Lewis acceptors has evolveds ignificantly in recent years, [1][2][3][4][5][6] with many analogies to the coordination chemistry of transition metal elements.I nt his context, we have recently reported complexes of Ph 3 Sb(OTf) 2 with classicalO -a nd N-donorl igands (Scheme1a).In contrast, attempts to isolate the correspondingc omplexes of Ph 3 Sb(OTf) 2 with Me 3 Pa saligand result in reduction of the antimony(V) centert oP h 3 Sb III and oxidation of the phosphine to [Me 3 PPMe 3 ][OTf] 2 (Scheme 1b), illustrating an oxidative PÀP coupling process or reductivee limination of ad iphosphonium dicationfrom antimony. [7] We have now discovered that in an analogousr eaction Ph 3 Sb(OTf) 2 effects oxidative SeÀSe coupling of trialkylphosphine selenides to give salts of 2 (Scheme1c). 31 P{ 1 H} NMR spectra of the respective reaction mixtures indicate that these reactions proceed via the coordination complexes 1(R 3 PSe) (Scheme 1c). Interestingly,N MR studies of the reactions of 2 with Ph 3 Sb (Scheme 1d)i ndicate that this redox process is reversible, demonstrating the versatilityo ft his redox behaviour of antimony.S imilar redox behaviour has only been reported for antimony in conjunctionw ithagold center,f or which Gabbai et al. reportedareversible umpolung of the SbÀAu bond upon reduction/oxidation. [8] Mixtures of two equivalentso fiPr 3 PSe with Ph 3 Sb(OTf) 2 in dichloromethane at RT show ab road signal in the 31 P{ 1 H} NMR spectrum (70.4 ppm, 1 J PSe = 663 Hz). The difference in chemical shift relative to the sharp signal for iPr 3 PSe (68.9 ppm) [9] is small,b ut when cooled to 187 K, three separates ignals are observed ( Figure 1).The most intense signal at 69.4 ppm ( 1 J PSe = 641 Hz) corresponds to free iPr 3 PSe. [9] the signal at 81.9 ppm ( 1 J PSe = 478 Hz) is assigned to 2(iPr), whichh as been successfully isolated and characterised, and the signal at 75.8 ppm ( 1 J PSe = 519 Hz) is assignedt ot he coordination complex 1(iPr 3 PSe). The phosphorus-selenium couplingc onstantss upport this assignment.T he 31 PNMR data and assignments for 1(iPr 3 PSe) are summarized in Ta ble 1.Mixtures of 2(iPr) with Ph 3 Sb, as in Scheme 1d,e xhibit 31 P{ 1 H} NMR signals that are consistentw ith those observed for 1(iPr 3 PSe) in Scheme 1c,i ndicating that this process is reversible. We conclude that mixtures of Ph 3 Sb(OTf) 2 with iPr 3 PSe form 1(iPr 3 PSe) whicha doptsa ne quilibrium with Ph 3 Sb and 2(iPr) (Scheme1c).A t2 98 Kt he exchange rate of the equilibrium leads to as ingle broad signal in the 31 P{ 1 H} NMRs pectrum, but at low temperatures the exchangei ss lower and individual signals for each component are observed.In acetonitrile, mixtures of iPr 3 PSe and Ph 3 Sb(OTf) 2 exhibita chemicals hift of 74.4 ppm, which we interpreta st he formation of 1(iPr 3 PSe) being more favouredi na cetonitrile than in dichloromethane, due to the higher basicity of acetonitrile in comparison to dichloromethane. Although acetonitrile is a betters olventf or the synthesis ...

Band Offsets, Optical Conduction, and Microwave Band Filtering Characteristics of γ‐In2Se3/CuO Heterojunctions

“…At the same time as the ionic radius of Cu (0.73 [ 12 ] ) is smaller than that of In, Cu can also occupy vacant sites of In (0.94 Å [ 13 ] ) at the ultrathin surface. In addition, the bond lengths of In—In, Se—Se, Cu—Cu, In—Se, Cu—Se, Cu—O, and In—O are 2.82, [ 14 ] 2.37, [ 15 ] 3.64, [ 16 ] 2.68, [ 17 ] 2.46, [ 18 ] 1.85, [ 19 ] and 2.16 Å, [ 20 ] respectively. When comparing bond lengths for In—Se and In—O one finds that the bond length for In—Se is larger than the bond length of In—O.…”

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes

“…57 Fe metal was purchased from EurIsotop (Cambridge Isotope Laboratories) and used as received. SePMe 3 , TePCy 3 (Cy = cyclohexyl), LH, 57 FeCl 2 , LFe(PhMe), L 2 Fe 2 S 2 ( 1 ox ) and [K(THF) 6 ][L 2 Fe 2 S 2 ]·2THF ( 1 ) were prepared as previously reported 27 , 46 – 50 .…”