Isolation of singlet carbene derived 2-arsa-1,3-butadiene radical cations and dications

2-Arsa-1,3-butadienes (L)As(cAACR) (L = PhC=C{(NDipp)CH}2, Dipp = 2,6-iPr2C6H3; cAACR = C{(NDipp)CMe2CH2C(R)}, R = Me22a, R = cyclohexyl (Cy) 2b) and the corresponding radical cations [(L)As(cAACR)]GaCl4 (R = Me23a, Cy 3b) and dications [(L)As(cAACR)](GaCl4)2 (R = Me 4a, Cy 4b) featuring a C=C–As=C π-conjugated framework are reported

Crystalline Divinyldiarsene Radical Cations and Dications

The divinyldiarsene radical cations [{(NHC)C(Ph)}As]2(GaCl4) (NHC=IPr: C{(NDipp)CH}2 3; SIPr: C{(NDipp)CH2}2 4; Dipp=2,6‐iPr2C6H3) and dications [{(NHC)C(Ph)}As]2(GaCl4)2 (NHC=IPr 5; SIPr 6) are readily accessible as crystalline solids on sequential one‐electron oxidation of the corresponding divinyldiarsenes [{(NHC)C(Ph)}As]2 (NHC=IPr 1; SIPr 2) with GaCl3. Compounds 3–6 have been characterized by X‐ray diffraction, cyclic voltammetry, EPR/NMR spectroscopy, and UV/vis absorption spectroscopy as well as DFT calculations. The sequential removal of one electron from the HOMO, that is mainly the As−As π‐bond, of 1 and 2 leads to successive elongation of the As=As bond and contraction of the C−As bonds from 1/2→3/4→5/6. The UV/vis spectrum of 3 and 4 each exhibits a strong absorption in the visible region associated with SOMO‐related transitions. The EPR spectrum of 3 and 4 each shows a broadened septet owing to coupling of the unpaired electron with two 75As (I=3/2) nuclei

Stable Silaimines with Three- and Four-Coordinate Silicon Atoms

Samuel PP, Azhakar R, Ghadwal R, et al. Stable Silaimines with Three- and Four-Coordinate Silicon Atoms. Inorganic Chemistry. 2012;51(20):11049-11054.The reactions of silylenes with organic azides are quite diverse, depending on the substituents of the silylene center and on the nature of the azide employed. Elusive silaimine with three-coordinate silicon atom L1SiN(2,6-Triip2-C6H3) (5) {L1 = CH[(C═CH2)(CMe)(2,6-iPr2C6H3N)2] and Triip = 2,4,6-triisopropylphenyl} was synthesized by treatment of the silylene L1Si (1) with a sterically demanding 2,6-bis(2,4,6-triisopropylphenyl)phenyl azide (2,6-Triip2C6H3N3). The reaction of Lewis base-stabilized dichlorosilylene L2SiCl2 (2) {L2 = 1,3-bis(2,6-iPr2C6H3)imidazol-2-ylidene} with Ph3SiN3 afforded four-coordinate silaimine L2(Cl2)SiNSiPh3 (6). Treatment of 2,6-Triip2C6H3N3 with L3SiCl (3) (L3 = PhC(NtBu)2) yielded silaimine L3(Cl)SiN(2,6-Triip2-C6H3) (7) possessing a four-coordinate silicon atom. The reactions of L3SiN(SiMe3)2 (4) with adamantyl and trimethylsilyl azide furnished silaimine compounds with a four-coordinate silicon atom L3(N(Ad)SiMe3)SiN(SiMe3) (8) (Ad = adamantyl) and L3(N(SiMe3)2)SiN(SiMe3) (9). Compound 8 was formed by migration of one of the SiMe3 groups. Compounds 5–9 are stable under inert atmosphere and were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray studies

Isolation of singlet carbene derived 2-phospha-1,3-butadienes and their sequential one-electron oxidation to radical cations and dications

A synthetic strategy for the 2-phospha-1,3-butadiene derivatives [{(IPr)C(Ph)}P(cAACMe)] (3a) and [{(IPr)C(Ph)}P(cAACCy)] (3b) (IPr = C{(NDipp)CH}2, Dipp = 2,6-iPr2C6H3; cAACMe = C{(NDipp)CMe2CH2CMe2}; cAACCy = C{(NDipp)CMe2CH2C(Cy)}, Cy = cyclohexyl) containing a C=C–P=C framework has been established. Compounds 3a and 3b have a remarkably small HOMO–LUMO energy gap (3a: 5.09; 3b: 5.05 eV) with a very high-lying HOMO (−4.95 eV for each). Consequently, 3a and 3b readily undergo one-electron oxidation with the mild oxidizing agent GaCl3 to afford radical cations [{(IPr)C(Ph)}P(cAACR)]GaCl4 (R = Me 4a, Cy 4b) as crystalline solids. The main UV-vis absorption band for 4a and 4b is red-shifted with respect to that of 3a and 3b, which is associated with the SOMO related transitions. The EPR spectra of compounds 4a and 4b each exhibit a doublet due to coupling of the unpaired electron with the 31P nucleus. Further one-electron removal from the radical cations 4a and 4b is also feasible with GaCl3, affording the dications [{(IPr)C(Ph)}P(cAACR)](GaCl4)2 (R = Me 5a, Cy 5b) as yellow crystals. The molecular structures of compounds 3–5 have been determined by X-ray diffraction and analyzed by DFT calculations