Crystalline Divinyldiarsenes and Cleavage of the As=As Bond

Abstract

The first divinyldiarsenes[ {(NHC)C(Ph)}As] 2 (NHC = IPr 3a,S IPr 3b;I Pr = C{(NAr)CH} 2 ;S IPr = C{(NAr)CH 2 } 2 ;A r = 2,6-iPr 2 C 6 H 3 )a re reported. Compounds 3a and 3b were prepared by the reduction of corresponding chlorides {(NHC)C(Ph)}AsCl 2 (NHC = IPr 2a,S IPr 2b)w ith Mg. Calculationsr evealed as mall HOMO-LUMO energy gap of 3.86 (3a)a nd 4.24 eV (3b). Treatment of 3a with (Me 2 S)AuCl led to the cleavage of the As=As bond to restore 2a,w hich is expected to proceed via the diarsane [{(IPr)C(Ph)}AsCl] 2 (4). Remarkably, 4 as wella s2a can be selectively accessed on treatment of 3a with an appropriate amount of C 2 Cl 6 .M oreover, 3a readily reacts with PhEEPh( E= Se or Te)a tr oom temperature to give {(IPr)C(-Ph)}As(EPh) 2 (E = Se 5a;T e5b), revealing the cleavageo f As=As and EÀEb onds and the formation of AsÀEb onds. Such highly selectivestepwise oxidation (3a!4!2a)a nd bond metathesis (3a!5a,b)r eactionsa re unprecedented in main-group chemistry.

A Modular Access to Divinyldiphosphenes with a Strikingly Small HOMO–LUMO Energy Gap

“…Deuterated solvents were dried over appropriate drying agents, distilled, and stored inside ag love box. NMR spectra were recorded on aB ruker Avance III 500 or aB ruker AvanceI II 500 HD spectrometer.C hemical shifts (in ppm) are referenced to the solvent residual signals:C 6 D 6 ( 1 H7 .16 ppm, 13 C{ 1 H} 128.06 ppm) and CDCl 3 ( 1 H7 .26 ppm, 13 C{ 1 H} 77.16 ppm). ESI mass spectra were recorded using an Esquire 3000 ion trap mass spectrometer (Bruker Daltonik GmbH, Bremen, Germany) equipped with an ano-ESI source.…”

“…It should, however, be noted that CAACs ( VII ) are stronger π‐acceptors compared with classical NHCs ( III ) . Therefore, a considerably higher π‐electron delocalization can be envisioned for compounds derived from NHCs ( III ) with respect to those with CAACs ( VII ) . This prompted us to reason that the NHC‐derived divinyldiphosphenes such as VIII would be an interesting structural modification to tailor the HOMO–LUMO energy gap with respect to CAAC derivatives VI .…”

“…[12] Therefore, ac onsiderably higher p-electron delocalization can be envisioned for compounds derived from NHCs (III)w ith respect to those with CAACs (VII). [13] This prompted us to reason that the NHC-derived divinyldiphosphenes such as VIII would be an interesting structural modification to tailor the HOMO-LUMO energy gap with respect to CAAC derivatives VI.H erein, we report amodularsynthetic strategy to access divinyldiphosphenes VIII using two new N-heterocyclic olefins (NHOs) 1 and 2.…”

Crystalline Divinyldiarsene Radical Cations and Dications

“…The high‐lying HOMO of III ‐E and Ar 3 As facilitates one‐electron oxidation giving rise to radical cations IV ‐E and V , respectively. We recently reported crystalline divinyldiarsenes 1 and 2 derived from classical NHCs, which exhibit remarkably small HOMO–LUMO energy gap of 3.86 eV and 4.24 eV, respectively . The high‐lying HOMO of 1 (−4.42 eV) and 2 (−5.28 eV) encouraged us to probe the synthetic viability of corresponding stable radical cations on one‐electron oxidation of 1 and 2 .…”

“…Solid‐state molecular structures of 3 (Figure ), 4 (Figure ), 5 (Figure ), and 6 (Supporting Information, Figure F8) were determined by X‐ray diffraction, which exhibit the intact As−As bond with trans ‐bent geometries along the two‐coordinated arsenic atoms. The HOMO of diarsenes 1 and 2 is the π‐orbital of the As=As bond . Thus, the formation of 3 and 4 as well as 5 and 6 is the result of sequential one electron removal from the HOMO of 1 and 2 .…”