Paresh Kumar Majhi

Synthesis, Structure, and Reactions of 1-tert-Butyl-2-diphenylphosphino-imidazole

Metalation reactions were studied of a sterically demanding imidazole derivative, namely, 1-tert-butylimidazole (1), with different metalation reagents and subsequent reaction with diphenylchlorophosphane. The reaction product, 1-tert-butyl-2-diphenylphosphino-imidazole (2), was subjected to oxidation and complexation reactions to yield the corresponding products Ph(2)(Imi)P-E (E = O (3), S (4), Se (5), W(CO)(5) (8)) and in the case of borane-THF the N-BH(3) coordination product 10 was obtained. The analytical data of the new compounds are discussed, including X-ray diffraction studies of 3-5.

Synthesis and Oxidative Desulfurization of PV-Functionalized Imidazole-2-thiones: Easy Access to P-Functional Ionic Liquids

Selective synthesis of 4-phosphanylated imidazole-2-thiones 2d, 3a,b(b′),c(c′),d were achieved using a backbone lithiation and phosphanylation reaction protocol. The 4-phosphanylated-imidazole-2-thiones 3b(b′),c(c′) were subjected to a oxidation/phosphanylation/oxidation reaction sequence to access C4/5-bis(phosphanoyl)-substituted imidazole-2-thiones 7b,c. Oxidative desulfurization of phosphanylated imidazole-2-thiones 2d, 4a,d, and 7b,c with hydrogen peroxide afforded the first examples of room temperature imidazolium ionic liquids 8d, 9a,d, and 10b,c respectively, possessing backbone P-substituents. To study the effect of the counter anion on the physical properties, imidazolium salts with counter anions such as Cl–, BF4–, PF6–, Tf2N–, and TfO– have been prepared by exchanging the counter anion of the obtained imidazolium hydrogen sulfates 8a,d and 14b with appropriate alkali or alkaline earth metal salts. All target products were characterised by various spectroscopic and spectrometric methods and by a single-crystal X-ray structure study in the case of 5a.

Synthesis of a 1-Aryl-2,2-chlorosilyl(phospha)silene Coordinated by an N-Heterocyclic Carbene

Phosphasilenes, P=Si doubly bonded compounds, have received considerable attention due to their unique physical and chemical properties. We report on the synthesis and structure of a chlorophosphasilene coordinated by an N-heterocyclic carbene (NHC), which has the potential of functionalization at the Si–Cl moiety. Treatment of a silylphosphine, ArPH–SiCl2RSi (Ar = bulky aryl group, RSi = Si(SiMe3)3) with two equivalents of Im-Me4 (1,3,4,5-tetramethylimidazol-2-ylidene) afforded the corresponding NHC-coordinated phosphasilene, ArP=SiClRSi(Im-Me4) as a stable compound. Bonding properties of the P=Si bond coordinated to an NHC will be discussed on the basis of theoretical calculations.

Tetrylones: An Intriguing Class of Monoatomic Zero-valent Group 14 Compounds

Tetrylones (ylidones) represent a class of zero-valent group 14 compounds with the general formula EL2 (E=C, Si, Ge, Sn, or Pb; L=neutral σ-donating ligand), wherein the tetrel atom, E(0), possess its four valence electrons in the form of two electron lone pairs, and is moreover coordinated by two ligands (L) via donor-acceptor interactions (L→E←L). This review focuses on the synthesis, structure, reactivity, and computational examination of the isolable heavier tetrylones (Si, Ge, Sn) that have been discovered recently. A comprehensive review on carbone chemistry is beyond the scope of this review. It should also be noted that tetrylones contain two different types of lone pairs, that is, one that exhibits p-type and one that exhibits s-type characteristics. Different behavior should thus be expected when these lone pairs react with Lewis acids.

Backbone Phosphonamide-Functionalized Imidazol-2-ylidene Complexes

The synthesis of M(CO)5 complexes bearing 4-phosphonamide and 4,5-bis(phosphonamide)-imidazol-2-ylidene ligands (NHCP = phosphonamide-based N-heterocyclic carbene) is reported. Deprotonation of respective imidazolium hydrogensulfate salts with potassium tert-butoxide (KOtBu) in the presence of [M(CO)5(CH3CN)] afforded complexes with the formula [M(CO)5(NHCP)]. In a similar fashion, reaction of in situ generated NHCP with [Rh(cod)Cl]2 (cod = 1,5-cyclooctadiene) afforded a complex with the formula [Rh(cod)Cl(NHCP)]. Low-temperature deprotonation of the imidazolium NHCP·H2SO4 with potassium hexamethyldisilazide (KHMDS) in the presence of [AuCl(SMe2)] furnished the corresponding AuI NHC complex. All complexes were characterized by various spectroscopic and spectrometric methods. In addition, further structural confirmation is provided by key single-crystal X-ray structure determinations for three of the new complexes.