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2019

73. Direct Functionalization of White Phosphorus with Anionic Dicarbenes and Mesoionic Carbenes: Facile Access to

       1,2,3-Triphosphol-2-ides

       D. Rottschäfer, S. Blomeyer, B. Neumann, H.-G. Stammler, R. S. Ghadwal*

    Chem. Sci. 2019, 10, 11078–11085.

Unprecedented [1+3] fragmentation of white phosphorus (P4) and thus the capturing of the P3+ fragment with anionic dicarbenes (ADCs) has been shown to afford the 1,2,3-triphosphol-2-ides I in 93-98% yield. The mesoionic heterocycles I feature 6π-electron C2P3 and C3N2 aromatic systems and serve as two-electron σ-donor ligands. 

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74. Electrophilic Terminal Arsinidene-Iron(0) Complexes with a Two-coordinated Arsenic Atom

       M. K. Sharma, B. Neumann, H.-G. Stammler, D. M. Andrada, R. S. Ghadwal*

    Chem. Commun. 2019, 55, 14669–14672.

The electrophilic arsinidene complexes 5 and 6 featuring a two-coordinated arsenic atom have been isolated as crystalline solids. Complex 5 readily reacts with an NHC nucleophile (IMe4) to give the Lewis adduct 7.

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72. Crystalline Divinyldiarsene Radical Cations and Dications

       M. K. Sharma, S. Blomeyer, B. Neumann, H.-G. Stammler, M. van Gastel, A. Hinz, R. S. Ghadwal* 

    Angew. Chem. Int. Ed. 2019, 58, 17599–17603.

One-by-one electron oxidation of diarsenes [As2] featuring very efficient π-donor N-heterocyclic vinyl substituents with GaCl3 leads to the formation of radical cations [As2] and dications [As2] as crystalline solids. Experimental and computational studies revealed the delocalization of unpaired electron over the π-conjugated CAs2C framework.

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71. Diphosphene radical cations and dications with a π-conjugated C2P2C2-framework

       M. K. Sharma, D. Rottschäfer, S. Blomeyer, B. Neumann, H.-G. Stammler, M. van Gastel, A. Hinz, R. S. Ghadwal* 

      Chem. Commun. 2019, 55, 10408–10411.

The synthesis and characterization of the crystalline diphosphene radical cations [{(NHC)C(Ph)}P]2(GaCl4)Ÿ (NHC = IPr = C{(NDipp)CH}2, SIPr = C{(NDipp)CH2}2; Dipp = 2,6-iPr2C6H3) and dications [{(NHC)C(Ph)}P]2(GaCl4)2 (NHC = IPr, SIPr) featuring a π-conjugated C2P2C2-framework has been reported.

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70. Stable Carbon-Centered Radicals Based on N-Heterocyclic Carbenes (Invited Article)

       R. S. Ghadwal*

      SynLett.  2019, 30,  1765-–1775.

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69. Crystalline Divinyldiarsenes and Cleavage of the As=As Bond

       M. K. Sharma, S. Blomeyer, B. Neumann, H.-G. Stammler, R. S. Ghadwal*

      Chem. Eur. J.  2019, 25,  8249–8253.

Making and breaking the As=As bond: The divinyldiarsene I (solid-state molecular structure: right) with a strikingly small HOMO-LUMO energy gap (3.86 eV) was prepared by the reduction of the dichloroarsane II. The As=As bond of I can be readily cleaved with C2Cl6, restoring II. This transformation is also viable with AuCl. Complex I endured oxidative bond metatheses with PhEEPh (E=Se or Te), producing derivatives III-E.

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68. A Modular Access to Divinyldiphosphenes with a Strikingly Small HOMO--LUMO Energy Gap

       D. Rottschäfer, M. K. Sharma, B. Neumann, H.-G. Stammler, D. M. Andrada, R. S. Ghadwal* 

      Chem. Eur. J.  2019, 25,  8127–8134.

P=P π-Conjugation: A modular synthetic route to the divinyldiphosphenes III with the smallest HOMO-LUMO energy gap (4.15 to 4.52 eV) has been established. Compounds III are accessible as deeply colored (inset) crystalline solids on reduction of the corresponding dichlorides II with magnesium. A divinyldiphosphene readily undergoes P=P bond cleavage reaction on treatment of S8 to give the rare vinyldithiophosphorane IV. (5: IPr-Derivative and 6: SIPr-Derivative.)

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67. A Phosphorus Analogue of p-Quinodimethane with a Planar P4 Ring: A Metal-Free Diphosphorus Source

        D. Rottschäfer, B. Neumann, H.-G. Stammler, R. Kishi, M. Nakano, R. S. Ghadwal* 

      Chem. Eur. J.  2019, 25, 3244–3247.

Metal-Free P2 Transfer: A phosphorus analogue of p-quinodimethane [(IPrC)2P4] (5) (IPr=1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) was readily accessible through KC8-reduction of (IPrC)(PCl2)2 (2). The P4 ring of 5 is perfectly planar and embedded with trans-apical N-heterocyclic vinylidene ligands. Compound 5 served as a metal-free diphosphorus (P2) source, which was captured with 1,3-cyclohexadiene (CHD), giving P2(CHD)2 (6).

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